diff --git a/packages/js/plugins/ws/README.md b/packages/js/plugins/ws/README.md
index ced32bc5d3..ea279f8d88 100644
--- a/packages/js/plugins/ws/README.md
+++ b/packages/js/plugins/ws/README.md
@@ -3,57 +3,9 @@
 WebSocket plugin allows Polywrap Client to interact with WebSocket servers.
 
 ## interface
-
-``` typescript
-# subset of JS MessageEvent interface
-type Message {
-    data: String!
-    origin: String!
-    lastEventId: String!
-}
-
-# path to WRAP method
-type Callback {
-    uri: String!,
-    method: String!
-}
-
-# optional fields are `Number | null` instead of `Option<i32>`
-type Number {
-    value: Int!
-}
-
-type Module {
-  # create a socket with id
-  ## can return after `timeout` if the server is not responding
-  open(url: String!, timeout: Number): Int!
-    
-  # close socket `id`
-  close(id: Int!): Boolean
-    
-  # send message via socket `id`
-  send(id: Int!, message: String!): Boolean
-    
-  # pass all messages to callback
-  addCallback(id: Int!, callback: Callback!): Boolean
-    
-  # stop passing messages to callback
-  removeCallback(id: Int!, callback: Callback!): Boolean
-    
-  # save messages to ws plugin cache
-  addCache(id: Int!): Boolean
-    
-  # stop caching messages
-  removeCache(id: Int!): Boolean
-    
-  # get [messages], flush cache
-  ## can wait until receives `min` events or reaches `timeout`
-  receive(id: Int!, min: Number, timeout: Number): [Message!]!
-}
-```
+See [schema.graphql](./src/schema.graphql).
 
 ## callback
-
 Every incoming WebSocket message can be passed to a callback function in another wrapper. Use `addCallback` to start passing messages and `removeCallback` to stop. The callback function is expected to have a parameter `data`, i.e. `foo(data: string)`.
 
 ``` typescript
diff --git a/packages/js/plugins/ws/src/__tests__/e2e/e2e.spec.ts b/packages/js/plugins/ws/src/__tests__/e2e/e2e.spec.ts
index b26c36605d..df8e969fd9 100644
--- a/packages/js/plugins/ws/src/__tests__/e2e/e2e.spec.ts
+++ b/packages/js/plugins/ws/src/__tests__/e2e/e2e.spec.ts
@@ -69,7 +69,7 @@ describe("WebSocket plugin", () => {
         method: "open",
         args: {
           url: "ws://localhost:1235",
-          timeout: { value: 50 }
+          timeout: 50
         }
       })
     });
@@ -347,7 +347,7 @@ describe("WebSocket plugin", () => {
         method: "receive",
         args: {
           id,
-          timeout: { value: 250 }
+          timeout: 250
         }
       })
 
@@ -378,7 +378,7 @@ describe("WebSocket plugin", () => {
         method: "receive",
         args: {
           id,
-          min: { value: 2 }
+          min: 2
         }
       })
 
@@ -408,8 +408,8 @@ describe("WebSocket plugin", () => {
         method: "receive",
         args: {
           id,
-          timeout: { value: 110 },
-          min: { value: 2 }
+          timeout: 110,
+          min: 2
         }
       })
 
@@ -439,8 +439,8 @@ describe("WebSocket plugin", () => {
         method: "receive",
         args: {
           id,
-          timeout: { value: 300 },
-          min: { value: 1 }
+          timeout: 300,
+          min: 1
         }
       })
 
diff --git a/packages/js/plugins/ws/src/__tests__/e2e/integration.spec.ts b/packages/js/plugins/ws/src/__tests__/e2e/integration.spec.ts
index db0292f602..4578dddeda 100644
--- a/packages/js/plugins/ws/src/__tests__/e2e/integration.spec.ts
+++ b/packages/js/plugins/ws/src/__tests__/e2e/integration.spec.ts
@@ -106,7 +106,7 @@ describe("e2e tests for WsPlugin", () => {
       class MemoryPlugin extends PluginModule<{}> {
         set(args: { key: string, value: string }, _client: Client): boolean {
           value[args.key] = args.value
-	  return true
+          return true
         }
         get(args: { key: string }, _client: Client): string | null {
           return value[args.key] ?? null
@@ -140,7 +140,7 @@ describe("e2e tests for WsPlugin", () => {
             uri,
             method: "callback"
           },
-	  message: "test"
+          message: "test"
         }
       });
 
diff --git a/packages/js/plugins/ws/src/__tests__/e2e/integration/schema.graphql b/packages/js/plugins/ws/src/__tests__/e2e/integration/schema.graphql
index 5ac685e4e5..1b1a3d2e74 100644
--- a/packages/js/plugins/ws/src/__tests__/e2e/integration/schema.graphql
+++ b/packages/js/plugins/ws/src/__tests__/e2e/integration/schema.graphql
@@ -24,6 +24,6 @@ type Module {
 
   get(
     url: String!,
-    timeout: Int!
+    timeout: UInt32!
   ): [String!]!
 }
diff --git a/packages/js/plugins/ws/src/__tests__/e2e/integration/src/index.ts b/packages/js/plugins/ws/src/__tests__/e2e/integration/src/index.ts
index e213428d5e..7345e8c726 100644
--- a/packages/js/plugins/ws/src/__tests__/e2e/integration/src/index.ts
+++ b/packages/js/plugins/ws/src/__tests__/e2e/integration/src/index.ts
@@ -7,6 +7,7 @@ import {
   Args_subscribeAndSend,
   Args_get
 } from "./wrap";
+import { Box } from "@polywrap/wasm-as";
 
 export function send(args: Args_send): boolean {
   const id = WS_Module.open({
@@ -68,9 +69,9 @@ export function get(args: Args_get): string[] {
 
   WS_Module.addCache({
     id
-  }).unwrap().unwrap()
+  }).unwrap()
 
-  const messages = WS_Module.receive({ id, timeout: { value: args.timeout } }).unwrap();
+  const messages = WS_Module.receive({ id, timeout: Box.from(args.timeout) }).unwrap();
 
   const data: string[] = messages.map<string>((msg) => msg.data);
 
diff --git a/packages/js/plugins/ws/src/index.ts b/packages/js/plugins/ws/src/index.ts
index e68e56851e..8f1a930018 100644
--- a/packages/js/plugins/ws/src/index.ts
+++ b/packages/js/plugins/ws/src/index.ts
@@ -32,7 +32,7 @@ export class WsPlugin extends Module<NoConfig> {
       if (args.timeout) {
         setTimeout(() => {
           reject(new Error("timeout reached"));
-        }, args.timeout.value);
+        }, args.timeout);
       }
       this._sockets[id].onopen = () => {
         resolve(id);
@@ -40,10 +40,7 @@ export class WsPlugin extends Module<NoConfig> {
     });
   }
 
-  public async close(
-    args: Args_close,
-    _client: Client
-  ): Promise<boolean | null> {
+  public async close(args: Args_close, _client: Client): Promise<boolean> {
     this._sockets[args.id].close();
     return await new Promise((resolve) => {
       this._sockets[args.id].onclose = () => {
@@ -52,12 +49,12 @@ export class WsPlugin extends Module<NoConfig> {
     });
   }
 
-  public send(args: Args_send, _client: Client): boolean | null {
+  public send(args: Args_send, _client: Client): boolean {
     this._sockets[args.id].send(args.message);
     return true;
   }
 
-  public addCallback(args: Args_addCallback, _client: Client): boolean | null {
+  public addCallback(args: Args_addCallback, _client: Client): boolean {
     const callbackId = this._callbackId(args.callback);
     this._callbacks[callbackId] = async (msg) => {
       await _client.invoke<{ callback: boolean }>({
@@ -73,10 +70,7 @@ export class WsPlugin extends Module<NoConfig> {
     return true;
   }
 
-  public removeCallback(
-    args: Args_removeCallback,
-    _client: Client
-  ): boolean | null {
+  public removeCallback(args: Args_removeCallback, _client: Client): boolean {
     const callbackId = this._callbackId(args.callback);
     this._sockets[args.id].removeEventListener(
       "message",
@@ -85,7 +79,7 @@ export class WsPlugin extends Module<NoConfig> {
     return true;
   }
 
-  public addCache(args: Args_addCache, _client: Client): boolean | null {
+  public addCache(args: Args_addCache, _client: Client): boolean {
     const callback = { uri: args.id.toString(), method: "cache" };
     const callbackId = this._callbackId(callback);
     this._caches[args.id] = [];
@@ -109,7 +103,7 @@ export class WsPlugin extends Module<NoConfig> {
     return true;
   }
 
-  public removeCache(args: Args_removeCache, _client: Client): boolean | null {
+  public removeCache(args: Args_removeCache, _client: Client): boolean {
     const callback = { uri: args.id.toString(), method: "cache" };
     const callbackId = this._callbackId(callback);
     this._sockets[args.id].removeEventListener(
@@ -135,7 +129,7 @@ export class WsPlugin extends Module<NoConfig> {
       if (args.min) {
         interval = setInterval(() => {
           if (args.min) {
-            if (this._caches[args.id].length >= args.min.value) {
+            if (this._caches[args.id].length >= args.min) {
               clearInterval(interval);
               clear();
             }
@@ -146,7 +140,7 @@ export class WsPlugin extends Module<NoConfig> {
         setTimeout(() => {
           clearInterval(interval);
           clear();
-        }, args.timeout.value);
+        }, args.timeout);
       }
       if (!args.timeout && !args.min) {
         clear();
diff --git a/packages/js/plugins/ws/src/schema.graphql b/packages/js/plugins/ws/src/schema.graphql
index 1f5f375777..d35469f91c 100644
--- a/packages/js/plugins/ws/src/schema.graphql
+++ b/packages/js/plugins/ws/src/schema.graphql
@@ -1,25 +1,57 @@
+"""Subset of JS MessageEvent interface"""
 type Message {
-    data: String!
-    origin: String!
-    lastEventId: String!
+  data: String!
+  origin: String!
+  lastEventId: String!
 }
 
 type Callback {
-    uri: String!,
-    method: String!
-}
-
-type Number {
-    value: Int!
+  """WRAP Module URI"""
+  uri: String!
+  """WRAP Module Method"""
+  method: String!
 }
 
 type Module {
-  open(url: String!, timeout: Number): Int!
-  close(id: Int!): Boolean
-  send(id: Int!, message: String!): Boolean
-  addCallback(id: Int!, callback: Callback!): Boolean
-  removeCallback(id: Int!, callback: Callback!): Boolean
-  addCache(id: Int!): Boolean
-  removeCache(id: Int!): Boolean
-  receive(id: Int!, min: Number, timeout: Number): [Message!]!
+  """
+  create a socket with id, can return after `timeout`
+  if the server is not responding. Returns the socket `id`
+  """
+  open(url: String!, timeout: UInt32): UInt32!
+
+  """
+  close socket `id`
+  """
+  close(id: UInt32!): Boolean!
+
+  """
+  send message via socket `id`
+  """
+  send(id: UInt32!, message: String!): Boolean!
+
+  """
+  send all messages to callback for socket `id`
+  """
+  addCallback(id: UInt32!, callback: Callback!): Boolean!
+
+  """
+  stop sending messages to callback for socket `id`
+  """
+  removeCallback(id: UInt32!, callback: Callback!): Boolean!
+
+  """
+  save messages to ws plugin cache for socket `id`
+  """
+  addCache(id: UInt32!): Boolean!
+
+  """
+  stop caching messages for socket `id`
+  """
+  removeCache(id: UInt32!): Boolean!
+
+  """
+  get messages and flush cache,
+  can wait until receives `min` events or reaches `timeout`
+  """
+  receive(id: UInt32!, min: UInt32, timeout: UInt32): [Message!]!
 }
diff --git a/packages/schema/bind/src/bindings/assemblyscript/functions.ts b/packages/schema/bind/src/bindings/assemblyscript/functions.ts
index 44c34685a7..f58c5d5e12 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/functions.ts
+++ b/packages/schema/bind/src/bindings/assemblyscript/functions.ts
@@ -51,14 +51,10 @@ export const toWasmInit: MustacheFn = () => {
       type = type.substring(0, type.length - 1);
     } else {
       const nullType = toWasm()(value, render);
-      const optional = "Option";
       const nullOptional = "| null";
 
       if (nullType.endsWith(nullOptional)) {
         return "null";
-      } else if (nullType.startsWith(optional)) {
-        type = nullType.substring(6);
-        return `Option.None${type}()`;
       }
     }
 
@@ -250,7 +246,7 @@ const applyOptional = (
     ) {
       return `${type} | null`;
     } else {
-      return `Option<${type}>`;
+      return `Box<${type}> | null`;
     }
   } else {
     return type;
diff --git a/packages/schema/bind/src/bindings/assemblyscript/types.ts b/packages/schema/bind/src/bindings/assemblyscript/types.ts
index 545f4611c1..6961a87298 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/types.ts
+++ b/packages/schema/bind/src/bindings/assemblyscript/types.ts
@@ -199,6 +199,9 @@ const keywords = {
   Float64Array: "Float64Array",
   TemplateStringsArray: "TemplateStringsArray",
   Error: "Error",
+  Result: "Result",
+  Box: "Box",
+  JSON: "JSON",
   // runtime
   abort: "abort",
   trace: "trace",
diff --git a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/deserialize_enum.mustache b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/deserialize_enum.mustache
index e45e533f3c..6702368f21 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/deserialize_enum.mustache
+++ b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/deserialize_enum.mustache
@@ -8,19 +8,19 @@ if (reader.isNextString()) {
 }
 {{/required}}
 {{^required}}
-let value: Option<Types.{{#detectKeyword}}{{type}}{{/detectKeyword}}>;
+let value: Box<Types.{{#detectKeyword}}{{type}}{{/detectKeyword}}> | null;
 if (!reader.isNextNil()) {
   if (reader.isNextString()) {
-    value = Option.Some(
+    value = Box.from(
       Types.get{{type}}Value(reader.readString())
     );
   } else {
-    value = Option.Some(
+    value = Box.from(
       reader.readInt32()
     );
     Types.sanitize{{type}}Value(value.unwrap());
   }
 } else {
-  value = Option.None<Types.{{#detectKeyword}}{{type}}{{/detectKeyword}}>();
+  value = null;
 }
 {{/required}}
diff --git a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/env-type/index-ts.mustache b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/env-type/index-ts.mustache
index 1bd693e9c0..8199149c0d 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/env-type/index-ts.mustache
+++ b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/env-type/index-ts.mustache
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/module-type/index-ts.mustache b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/module-type/index-ts.mustache
index 46c901b31f..ed45b7686e 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/module-type/index-ts.mustache
+++ b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/module-type/index-ts.mustache
@@ -1,7 +1,7 @@
 import {
   wrap_subinvoke,
   wrap_subinvokeImplementation,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/object-type/index-ts.mustache b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/object-type/index-ts.mustache
index bd6dec16ce..3d914e5ae1 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/object-type/index-ts.mustache
+++ b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/imported/object-type/index-ts.mustache
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/object-type/index-ts.mustache b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/object-type/index-ts.mustache
index 1bd693e9c0..8199149c0d 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/object-type/index-ts.mustache
+++ b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/object-type/index-ts.mustache
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/serialization_imports.mustache b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/serialization_imports.mustache
index 9ded19f5d4..933d73f458 100644
--- a/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/serialization_imports.mustache
+++ b/packages/schema/bind/src/bindings/assemblyscript/wasm/templates/serialization_imports.mustache
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/templates/package.json b/packages/templates/package.json
index 98c2ddb572..6bc9138bc4 100644
--- a/packages/templates/package.json
+++ b/packages/templates/package.json
@@ -8,7 +8,9 @@
     "url": "https://github.com/polywrap/monorepo.git"
   },
   "scripts": {
-    "test": "jest --passWithNoTests --runInBand --verbose",
+    "wasm-linked:up": "cp ./polywrap.wasm-linked* ./wasm/assemblyscript/",
+    "wasm-linked:down": "rm ./wasm/assemblyscript/polywrap.wasm-linked*",
+    "test": "yarn wasm-linked:up; jest --passWithNoTests --runInBand --verbose; yarn wasm-linked:down",
     "test:ci": "yarn test"
   },
   "devDependencies": {
diff --git a/packages/templates/polywrap.wasm-linked.build.yaml b/packages/templates/polywrap.wasm-linked.build.yaml
new file mode 100644
index 0000000000..959488ab0c
--- /dev/null
+++ b/packages/templates/polywrap.wasm-linked.build.yaml
@@ -0,0 +1,11 @@
+format: 0.1.0
+docker:
+  name: template-wasm-as
+config:
+  node_version: "16.13.0"
+  include:
+    - ./package.json
+    - ./src
+linked_packages:
+  - name: "@polywrap/wasm-as"
+    path: ../../../wasm/as
diff --git a/packages/templates/polywrap.wasm-linked.yaml b/packages/templates/polywrap.wasm-linked.yaml
new file mode 100644
index 0000000000..294a567ae7
--- /dev/null
+++ b/packages/templates/polywrap.wasm-linked.yaml
@@ -0,0 +1,9 @@
+format: 0.2.0
+project:
+  name: template-wasm-as
+  type: wasm/assemblyscript
+source:
+  module: ./src/index.ts
+  schema: ./src/schema.graphql
+extensions:
+  build: ./polywrap.wasm-linked.build.yaml
diff --git a/packages/templates/tests.spec.ts b/packages/templates/tests.spec.ts
index 0285699310..248c72102c 100644
--- a/packages/templates/tests.spec.ts
+++ b/packages/templates/tests.spec.ts
@@ -21,7 +21,7 @@ describe("Templates", () => {
       build: "CI=false yarn build",
     },
     assemblyscript: {
-      build: "yarn build",
+      build: "npx polywrap build -m ./polywrap.wasm-linked.yaml",
       test: "yarn test:e2e",
     },
     rust: {
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/index.ts
index f0078d83b9..7d2d0c8391 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/serialization.ts
index 4bf9c7a830..9ed99bc7a3 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/AnotherType/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/index.ts
index 16e451dd4e..4162a95785 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/serialization.ts
index 847dde1269..d3f1ee9fb8 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomMapValue/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/index.ts
index 917c30a1be..64b2cdf31c 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
@@ -18,7 +18,7 @@ export class CustomType {
   str: string;
   optStr: string | null;
   u: u32;
-  optU: Option<u32>;
+  optU: Box<u32> | null;
   _u8: u8;
   _u16: u16;
   _u32: u32;
@@ -35,13 +35,13 @@ export class CustomType {
   bytes: ArrayBuffer;
   optBytes: ArrayBuffer | null;
   _boolean: bool;
-  optBoolean: Option<bool>;
+  optBoolean: Box<bool> | null;
   uArray: Array<u32>;
   uOptArray: Array<u32> | null;
-  optUOptArray: Array<Option<u32>> | null;
+  optUOptArray: Array<Box<u32> | null> | null;
   optStrOptArray: Array<string | null> | null;
   uArrayArray: Array<Array<u32>>;
-  uOptArrayOptArray: Array<Array<Option<u32>> | null>;
+  uOptArrayOptArray: Array<Array<Box<u32> | null> | null>;
   uArrayOptArrayArray: Array<Array<Array<u32>> | null>;
   crazyArray: Array<Array<Array<Array<u32> | null>> | null> | null;
   object: Types.AnotherType;
@@ -49,9 +49,9 @@ export class CustomType {
   objectArray: Array<Types.AnotherType>;
   optObjectArray: Array<Types.AnotherType | null> | null;
   en: Types.CustomEnum;
-  optEnum: Option<Types.CustomEnum>;
+  optEnum: Box<Types.CustomEnum> | null;
   enumArray: Array<Types.CustomEnum>;
-  optEnumArray: Array<Option<Types.CustomEnum>> | null;
+  optEnumArray: Array<Box<Types.CustomEnum> | null> | null;
   map: Map<string, i32>;
   mapOfArr: Map<string, Array<i32>>;
   mapOfObj: Map<string, Types.AnotherType>;
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/serialization.ts
index e033193852..b555b83786 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/CustomType/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
@@ -38,7 +38,7 @@ export function writeCustomType(writer: Write, type: CustomType): void {
   writer.writeString("u");
   writer.writeUInt32(type.u);
   writer.context().pop();
-  writer.context().push("optU", "Option<u32>", "writing property");
+  writer.context().push("optU", "Box<u32> | null", "writing property");
   writer.writeString("optU");
   writer.writeOptionalUInt32(type.optU);
   writer.context().pop();
@@ -106,7 +106,7 @@ export function writeCustomType(writer: Write, type: CustomType): void {
   writer.writeString("boolean");
   writer.writeBool(type._boolean);
   writer.context().pop();
-  writer.context().push("optBoolean", "Option<bool>", "writing property");
+  writer.context().push("optBoolean", "Box<bool> | null", "writing property");
   writer.writeString("optBoolean");
   writer.writeOptionalBool(type.optBoolean);
   writer.context().pop();
@@ -122,9 +122,9 @@ export function writeCustomType(writer: Write, type: CustomType): void {
     writer.writeUInt32(item);
   });
   writer.context().pop();
-  writer.context().push("optUOptArray", "Array<Option<u32>> | null", "writing property");
+  writer.context().push("optUOptArray", "Array<Box<u32> | null> | null", "writing property");
   writer.writeString("optUOptArray");
-  writer.writeOptionalArray(type.optUOptArray, (writer: Write, item: Option<u32>): void => {
+  writer.writeOptionalArray(type.optUOptArray, (writer: Write, item: Box<u32> | null): void => {
     writer.writeOptionalUInt32(item);
   });
   writer.context().pop();
@@ -142,10 +142,10 @@ export function writeCustomType(writer: Write, type: CustomType): void {
     });
   });
   writer.context().pop();
-  writer.context().push("uOptArrayOptArray", "Array<Array<Option<u32>> | null>", "writing property");
+  writer.context().push("uOptArrayOptArray", "Array<Array<Box<u32> | null> | null>", "writing property");
   writer.writeString("uOptArrayOptArray");
-  writer.writeArray(type.uOptArrayOptArray, (writer: Write, item: Array<Option<u32>> | null): void => {
-    writer.writeOptionalArray(item, (writer: Write, item: Option<u32>): void => {
+  writer.writeArray(type.uOptArrayOptArray, (writer: Write, item: Array<Box<u32> | null> | null): void => {
+    writer.writeOptionalArray(item, (writer: Write, item: Box<u32> | null): void => {
       writer.writeOptionalUInt32(item);
     });
   });
@@ -204,7 +204,7 @@ export function writeCustomType(writer: Write, type: CustomType): void {
   writer.writeString("en");
   writer.writeInt32(type.en);
   writer.context().pop();
-  writer.context().push("optEnum", "Option<Types.CustomEnum>", "writing property");
+  writer.context().push("optEnum", "Box<Types.CustomEnum> | null", "writing property");
   writer.writeString("optEnum");
   writer.writeOptionalInt32(type.optEnum);
   writer.context().pop();
@@ -214,9 +214,9 @@ export function writeCustomType(writer: Write, type: CustomType): void {
     writer.writeInt32(item);
   });
   writer.context().pop();
-  writer.context().push("optEnumArray", "Array<Option<Types.CustomEnum>> | null", "writing property");
+  writer.context().push("optEnumArray", "Array<Box<Types.CustomEnum> | null> | null", "writing property");
   writer.writeString("optEnumArray");
-  writer.writeOptionalArray(type.optEnumArray, (writer: Write, item: Option<Types.CustomEnum>): void => {
+  writer.writeOptionalArray(type.optEnumArray, (writer: Write, item: Box<Types.CustomEnum> | null): void => {
     writer.writeOptionalInt32(item);
   });
   writer.context().pop();
@@ -284,7 +284,7 @@ export function readCustomType(reader: Read): CustomType {
   let _optStr: string | null = null;
   let _u: u32 = 0;
   let _uSet: bool = false;
-  let _optU: Option<u32> = Option.None<u32>();
+  let _optU: Box<u32> | null = null;
   let _u8: u8 = 0;
   let _u8Set: bool = false;
   let _u16: u16 = 0;
@@ -313,15 +313,15 @@ export function readCustomType(reader: Read): CustomType {
   let _optBytes: ArrayBuffer | null = null;
   let _boolean: bool = false;
   let _booleanSet: bool = false;
-  let _optBoolean: Option<bool> = Option.None<bool>();
+  let _optBoolean: Box<bool> | null = null;
   let _uArray: Array<u32> = [];
   let _uArraySet: bool = false;
   let _uOptArray: Array<u32> | null = null;
-  let _optUOptArray: Array<Option<u32>> | null = null;
+  let _optUOptArray: Array<Box<u32> | null> | null = null;
   let _optStrOptArray: Array<string | null> | null = null;
   let _uArrayArray: Array<Array<u32>> = [];
   let _uArrayArraySet: bool = false;
-  let _uOptArrayOptArray: Array<Array<Option<u32>> | null> = [];
+  let _uOptArrayOptArray: Array<Array<Box<u32> | null> | null> = [];
   let _uOptArrayOptArraySet: bool = false;
   let _uArrayOptArrayArray: Array<Array<Array<u32>> | null> = [];
   let _uArrayOptArrayArraySet: bool = false;
@@ -334,10 +334,10 @@ export function readCustomType(reader: Read): CustomType {
   let _optObjectArray: Array<Types.AnotherType | null> | null = null;
   let _en: Types.CustomEnum = 0;
   let _enSet: bool = false;
-  let _optEnum: Option<Types.CustomEnum> = Option.None<Types.CustomEnum>();
+  let _optEnum: Box<Types.CustomEnum> | null = null;
   let _enumArray: Array<Types.CustomEnum> = [];
   let _enumArraySet: bool = false;
-  let _optEnumArray: Array<Option<Types.CustomEnum>> | null = null;
+  let _optEnumArray: Array<Box<Types.CustomEnum> | null> | null = null;
   let _map: Map<string, i32> = new Map<string, i32>();
   let _mapSet: bool = false;
   let _mapOfArr: Map<string, Array<i32>> = new Map<string, Array<i32>>();
@@ -372,7 +372,7 @@ export function readCustomType(reader: Read): CustomType {
       reader.context().pop();
     }
     else if (field == "optU") {
-      reader.context().push(field, "Option<u32>", "type found, reading property");
+      reader.context().push(field, "Box<u32> | null", "type found, reading property");
       _optU = reader.readOptionalUInt32();
       reader.context().pop();
     }
@@ -469,7 +469,7 @@ export function readCustomType(reader: Read): CustomType {
       reader.context().pop();
     }
     else if (field == "optBoolean") {
-      reader.context().push(field, "Option<bool>", "type found, reading property");
+      reader.context().push(field, "Box<bool> | null", "type found, reading property");
       _optBoolean = reader.readOptionalBool();
       reader.context().pop();
     }
@@ -489,8 +489,8 @@ export function readCustomType(reader: Read): CustomType {
       reader.context().pop();
     }
     else if (field == "optUOptArray") {
-      reader.context().push(field, "Array<Option<u32>> | null", "type found, reading property");
-      _optUOptArray = reader.readOptionalArray((reader: Read): Option<u32> => {
+      reader.context().push(field, "Array<Box<u32> | null> | null", "type found, reading property");
+      _optUOptArray = reader.readOptionalArray((reader: Read): Box<u32> | null => {
         return reader.readOptionalUInt32();
       });
       reader.context().pop();
@@ -513,9 +513,9 @@ export function readCustomType(reader: Read): CustomType {
       reader.context().pop();
     }
     else if (field == "uOptArrayOptArray") {
-      reader.context().push(field, "Array<Array<Option<u32>> | null>", "type found, reading property");
-      _uOptArrayOptArray = reader.readArray((reader: Read): Array<Option<u32>> | null => {
-        return reader.readOptionalArray((reader: Read): Option<u32> => {
+      reader.context().push(field, "Array<Array<Box<u32> | null> | null>", "type found, reading property");
+      _uOptArrayOptArray = reader.readArray((reader: Read): Array<Box<u32> | null> | null => {
+        return reader.readOptionalArray((reader: Read): Box<u32> | null => {
           return reader.readOptionalUInt32();
         });
       });
@@ -597,21 +597,21 @@ export function readCustomType(reader: Read): CustomType {
       reader.context().pop();
     }
     else if (field == "optEnum") {
-      reader.context().push(field, "Option<Types.CustomEnum>", "type found, reading property");
-      let value: Option<Types.CustomEnum>;
+      reader.context().push(field, "Box<Types.CustomEnum> | null", "type found, reading property");
+      let value: Box<Types.CustomEnum> | null;
       if (!reader.isNextNil()) {
         if (reader.isNextString()) {
-          value = Option.Some(
+          value = Box.from(
             Types.getCustomEnumValue(reader.readString())
           );
         } else {
-          value = Option.Some(
+          value = Box.from(
             reader.readInt32()
           );
           Types.sanitizeCustomEnumValue(value.unwrap());
         }
       } else {
-        value = Option.None<Types.CustomEnum>();
+        value = null;
       }
       _optEnum = value;
       reader.context().pop();
@@ -632,22 +632,22 @@ export function readCustomType(reader: Read): CustomType {
       reader.context().pop();
     }
     else if (field == "optEnumArray") {
-      reader.context().push(field, "Array<Option<Types.CustomEnum>> | null", "type found, reading property");
-      _optEnumArray = reader.readOptionalArray((reader: Read): Option<Types.CustomEnum> => {
-        let value: Option<Types.CustomEnum>;
+      reader.context().push(field, "Array<Box<Types.CustomEnum> | null> | null", "type found, reading property");
+      _optEnumArray = reader.readOptionalArray((reader: Read): Box<Types.CustomEnum> | null => {
+        let value: Box<Types.CustomEnum> | null;
         if (!reader.isNextNil()) {
           if (reader.isNextString()) {
-            value = Option.Some(
+            value = Box.from(
               Types.getCustomEnumValue(reader.readString())
             );
           } else {
-            value = Option.Some(
+            value = Box.from(
               reader.readInt32()
             );
             Types.sanitizeCustomEnumValue(value.unwrap());
           }
         } else {
-          value = Option.None<Types.CustomEnum>();
+          value = null;
         }
         return value;
       });
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/index.ts
index e23475d9bf..6e9417c587 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
@@ -17,7 +17,7 @@ import * as Types from "..";
 export class Env {
   prop: string;
   optProp: string | null;
-  optMap: Map<string, Option<i32>> | null;
+  optMap: Map<string, Box<i32> | null> | null;
 
   static toBuffer(type: Env): ArrayBuffer {
     return serializeEnv(type);
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/serialization.ts
index b6fbadfd37..84186a0ea1 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/Env/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
@@ -34,11 +34,11 @@ export function writeEnv(writer: Write, type: Env): void {
   writer.writeString("optProp");
   writer.writeOptionalString(type.optProp);
   writer.context().pop();
-  writer.context().push("optMap", "Map<string, Option<i32>> | null", "writing property");
+  writer.context().push("optMap", "Map<string, Box<i32> | null> | null", "writing property");
   writer.writeString("optMap");
   writer.writeOptionalExtGenericMap(type.optMap, (writer: Write, key: string) => {
     writer.writeString(key);
-  }, (writer: Write, value: Option<i32>): void => {
+  }, (writer: Write, value: Box<i32> | null): void => {
     writer.writeOptionalInt32(value);
   });
   writer.context().pop();
@@ -56,7 +56,7 @@ export function readEnv(reader: Read): Env {
   let _prop: string = "";
   let _propSet: bool = false;
   let _optProp: string | null = null;
-  let _optMap: Map<string, Option<i32>> | null = null;
+  let _optMap: Map<string, Box<i32> | null> | null = null;
 
   while (numFields > 0) {
     numFields--;
@@ -75,10 +75,10 @@ export function readEnv(reader: Read): Env {
       reader.context().pop();
     }
     else if (field == "optMap") {
-      reader.context().push(field, "Map<string, Option<i32>> | null", "type found, reading property");
+      reader.context().push(field, "Map<string, Box<i32> | null> | null", "type found, reading property");
       _optMap = reader.readOptionalExtGenericMap((reader: Read): string => {
         return reader.readString();
-      }, (reader: Read): Option<i32> => {
+      }, (reader: Read): Box<i32> | null => {
         return reader.readOptionalInt32();
       });
       reader.context().pop();
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/Module/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/Module/serialization.ts
index 4fe8792357..d33172ef42 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/Module/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/Module/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
@@ -16,9 +16,9 @@ export class Args_moduleMethod {
   str: string;
   optStr: string | null;
   en: Types.CustomEnum;
-  optEnum: Option<Types.CustomEnum>;
+  optEnum: Box<Types.CustomEnum> | null;
   enumArray: Array<Types.CustomEnum>;
-  optEnumArray: Array<Option<Types.CustomEnum>> | null;
+  optEnumArray: Array<Box<Types.CustomEnum> | null> | null;
   map: Map<string, i32>;
   mapOfArr: Map<string, Array<i32>>;
   mapOfMap: Map<string, Map<string, i32>>;
@@ -36,10 +36,10 @@ export function deserializemoduleMethodArgs(argsBuf: ArrayBuffer): Args_moduleMe
   let _optStr: string | null = null;
   let _en: Types.CustomEnum = 0;
   let _enSet: bool = false;
-  let _optEnum: Option<Types.CustomEnum> = Option.None<Types.CustomEnum>();
+  let _optEnum: Box<Types.CustomEnum> | null = null;
   let _enumArray: Array<Types.CustomEnum> = [];
   let _enumArraySet: bool = false;
-  let _optEnumArray: Array<Option<Types.CustomEnum>> | null = null;
+  let _optEnumArray: Array<Box<Types.CustomEnum> | null> | null = null;
   let _map: Map<string, i32> = new Map<string, i32>();
   let _mapSet: bool = false;
   let _mapOfArr: Map<string, Array<i32>> = new Map<string, Array<i32>>();
@@ -81,21 +81,21 @@ export function deserializemoduleMethodArgs(argsBuf: ArrayBuffer): Args_moduleMe
       reader.context().pop();
     }
     else if (field == "optEnum") {
-      reader.context().push(field, "Option<Types.CustomEnum>", "type found, reading property");
-      let value: Option<Types.CustomEnum>;
+      reader.context().push(field, "Box<Types.CustomEnum> | null", "type found, reading property");
+      let value: Box<Types.CustomEnum> | null;
       if (!reader.isNextNil()) {
         if (reader.isNextString()) {
-          value = Option.Some(
+          value = Box.from(
             Types.getCustomEnumValue(reader.readString())
           );
         } else {
-          value = Option.Some(
+          value = Box.from(
             reader.readInt32()
           );
           Types.sanitizeCustomEnumValue(value.unwrap());
         }
       } else {
-        value = Option.None<Types.CustomEnum>();
+        value = null;
       }
       _optEnum = value;
       reader.context().pop();
@@ -116,22 +116,22 @@ export function deserializemoduleMethodArgs(argsBuf: ArrayBuffer): Args_moduleMe
       reader.context().pop();
     }
     else if (field == "optEnumArray") {
-      reader.context().push(field, "Array<Option<Types.CustomEnum>> | null", "type found, reading property");
-      _optEnumArray = reader.readOptionalArray((reader: Read): Option<Types.CustomEnum> => {
-        let value: Option<Types.CustomEnum>;
+      reader.context().push(field, "Array<Box<Types.CustomEnum> | null> | null", "type found, reading property");
+      _optEnumArray = reader.readOptionalArray((reader: Read): Box<Types.CustomEnum> | null => {
+        let value: Box<Types.CustomEnum> | null;
         if (!reader.isNextNil()) {
           if (reader.isNextString()) {
-            value = Option.Some(
+            value = Box.from(
               Types.getCustomEnumValue(reader.readString())
             );
           } else {
-            value = Option.Some(
+            value = Box.from(
               reader.readInt32()
             );
             Types.sanitizeCustomEnumValue(value.unwrap());
           }
         } else {
-          value = Option.None<Types.CustomEnum>();
+          value = null;
         }
         return value;
       });
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/else/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/else/index.ts
index e3b07794d9..48f590f30b 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/else/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/else/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/else/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/else/serialization.ts
index f89184e286..08a0df0df3 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/else/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/else/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/index.ts
index 8957633043..54d80f554c 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/serialization.ts
index 98b67d08ff..1835851b49 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_AnotherObject/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Env/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Env/serialization.ts
index aff902a1bb..48866a4a00 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Env/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Env/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/index.ts
index 1f5887a141..86b76df375 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/index.ts
@@ -1,7 +1,7 @@
 import {
   wrap_subinvoke,
   wrap_subinvokeImplementation,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/serialization.ts
index c6b5c83eaa..b2efd2df5e 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Module/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
@@ -16,16 +16,16 @@ export class Args_importedMethod {
   str: string;
   optStr: string | null;
   u: u32;
-  optU: Option<u32>;
-  uArrayArray: Array<Array<Option<u32>> | null>;
+  optU: Box<u32> | null;
+  uArrayArray: Array<Array<Box<u32> | null> | null>;
   object: Types.TestImport_Object;
   optObject: Types.TestImport_Object | null;
   objectArray: Array<Types.TestImport_Object>;
   optObjectArray: Array<Types.TestImport_Object | null> | null;
   en: Types.TestImport_Enum;
-  optEnum: Option<Types.TestImport_Enum>;
+  optEnum: Box<Types.TestImport_Enum> | null;
   enumArray: Array<Types.TestImport_Enum>;
-  optEnumArray: Array<Option<Types.TestImport_Enum>> | null;
+  optEnumArray: Array<Box<Types.TestImport_Enum> | null> | null;
 }
 
 export function serializeimportedMethodArgs(args: Args_importedMethod): ArrayBuffer {
@@ -56,14 +56,14 @@ export function writeimportedMethodArgs(
   writer.writeString("u");
   writer.writeUInt32(args.u);
   writer.context().pop();
-  writer.context().push("optU", "Option<u32>", "writing property");
+  writer.context().push("optU", "Box<u32> | null", "writing property");
   writer.writeString("optU");
   writer.writeOptionalUInt32(args.optU);
   writer.context().pop();
-  writer.context().push("uArrayArray", "Array<Array<Option<u32>> | null>", "writing property");
+  writer.context().push("uArrayArray", "Array<Array<Box<u32> | null> | null>", "writing property");
   writer.writeString("uArrayArray");
-  writer.writeArray(args.uArrayArray, (writer: Write, item: Array<Option<u32>> | null): void => {
-    writer.writeOptionalArray(item, (writer: Write, item: Option<u32>): void => {
+  writer.writeArray(args.uArrayArray, (writer: Write, item: Array<Box<u32> | null> | null): void => {
+    writer.writeOptionalArray(item, (writer: Write, item: Box<u32> | null): void => {
       writer.writeOptionalUInt32(item);
     });
   });
@@ -100,7 +100,7 @@ export function writeimportedMethodArgs(
   writer.writeString("en");
   writer.writeInt32(args.en);
   writer.context().pop();
-  writer.context().push("optEnum", "Option<Types.TestImport_Enum>", "writing property");
+  writer.context().push("optEnum", "Box<Types.TestImport_Enum> | null", "writing property");
   writer.writeString("optEnum");
   writer.writeOptionalInt32(args.optEnum);
   writer.context().pop();
@@ -110,9 +110,9 @@ export function writeimportedMethodArgs(
     writer.writeInt32(item);
   });
   writer.context().pop();
-  writer.context().push("optEnumArray", "Array<Option<Types.TestImport_Enum>> | null", "writing property");
+  writer.context().push("optEnumArray", "Array<Box<Types.TestImport_Enum> | null> | null", "writing property");
   writer.writeString("optEnumArray");
-  writer.writeOptionalArray(args.optEnumArray, (writer: Write, item: Option<Types.TestImport_Enum>): void => {
+  writer.writeOptionalArray(args.optEnumArray, (writer: Write, item: Box<Types.TestImport_Enum> | null): void => {
     writer.writeOptionalInt32(item);
   });
   writer.context().pop();
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/index.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/index.ts
index f15d8a58de..984be2af32 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/index.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/index.ts
@@ -1,7 +1,7 @@
 import {
   Read,
   Write,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON
@@ -23,9 +23,9 @@ export class TestImport_Object {
   objectArray: Array<Types.TestImport_AnotherObject>;
   optObjectArray: Array<Types.TestImport_AnotherObject | null> | null;
   en: Types.TestImport_Enum;
-  optEnum: Option<Types.TestImport_Enum>;
+  optEnum: Box<Types.TestImport_Enum> | null;
   enumArray: Array<Types.TestImport_Enum>;
-  optEnumArray: Array<Option<Types.TestImport_Enum>> | null;
+  optEnumArray: Array<Box<Types.TestImport_Enum> | null> | null;
 
   static toBuffer(type: TestImport_Object): ArrayBuffer {
     return serializeTestImport_Object(type);
diff --git a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/serialization.ts b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/serialization.ts
index 423b9b892b..b243ba964a 100644
--- a/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/serialization.ts
+++ b/packages/test-cases/cases/bind/sanity/output/wasm-as/imported/TestImport_Object/serialization.ts
@@ -4,7 +4,7 @@ import {
   Write,
   WriteSizer,
   WriteEncoder,
-  Option,
+  Box,
   BigInt,
   BigNumber,
   JSON,
@@ -58,7 +58,7 @@ export function writeTestImport_Object(writer: Write, type: TestImport_Object):
   writer.writeString("en");
   writer.writeInt32(type.en);
   writer.context().pop();
-  writer.context().push("optEnum", "Option<Types.TestImport_Enum>", "writing property");
+  writer.context().push("optEnum", "Box<Types.TestImport_Enum> | null", "writing property");
   writer.writeString("optEnum");
   writer.writeOptionalInt32(type.optEnum);
   writer.context().pop();
@@ -68,9 +68,9 @@ export function writeTestImport_Object(writer: Write, type: TestImport_Object):
     writer.writeInt32(item);
   });
   writer.context().pop();
-  writer.context().push("optEnumArray", "Array<Option<Types.TestImport_Enum>> | null", "writing property");
+  writer.context().push("optEnumArray", "Array<Box<Types.TestImport_Enum> | null> | null", "writing property");
   writer.writeString("optEnumArray");
-  writer.writeOptionalArray(type.optEnumArray, (writer: Write, item: Option<Types.TestImport_Enum>): void => {
+  writer.writeOptionalArray(type.optEnumArray, (writer: Write, item: Box<Types.TestImport_Enum> | null): void => {
     writer.writeOptionalInt32(item);
   });
   writer.context().pop();
@@ -93,10 +93,10 @@ export function readTestImport_Object(reader: Read): TestImport_Object {
   let _optObjectArray: Array<Types.TestImport_AnotherObject | null> | null = null;
   let _en: Types.TestImport_Enum = 0;
   let _enSet: bool = false;
-  let _optEnum: Option<Types.TestImport_Enum> = Option.None<Types.TestImport_Enum>();
+  let _optEnum: Box<Types.TestImport_Enum> | null = null;
   let _enumArray: Array<Types.TestImport_Enum> = [];
   let _enumArraySet: bool = false;
-  let _optEnumArray: Array<Option<Types.TestImport_Enum>> | null = null;
+  let _optEnumArray: Array<Box<Types.TestImport_Enum> | null> | null = null;
 
   while (numFields > 0) {
     numFields--;
@@ -153,21 +153,21 @@ export function readTestImport_Object(reader: Read): TestImport_Object {
       reader.context().pop();
     }
     else if (field == "optEnum") {
-      reader.context().push(field, "Option<Types.TestImport_Enum>", "type found, reading property");
-      let value: Option<Types.TestImport_Enum>;
+      reader.context().push(field, "Box<Types.TestImport_Enum> | null", "type found, reading property");
+      let value: Box<Types.TestImport_Enum> | null;
       if (!reader.isNextNil()) {
         if (reader.isNextString()) {
-          value = Option.Some(
+          value = Box.from(
             Types.getTestImport_EnumValue(reader.readString())
           );
         } else {
-          value = Option.Some(
+          value = Box.from(
             reader.readInt32()
           );
           Types.sanitizeTestImport_EnumValue(value.unwrap());
         }
       } else {
-        value = Option.None<Types.TestImport_Enum>();
+        value = null;
       }
       _optEnum = value;
       reader.context().pop();
@@ -188,22 +188,22 @@ export function readTestImport_Object(reader: Read): TestImport_Object {
       reader.context().pop();
     }
     else if (field == "optEnumArray") {
-      reader.context().push(field, "Array<Option<Types.TestImport_Enum>> | null", "type found, reading property");
-      _optEnumArray = reader.readOptionalArray((reader: Read): Option<Types.TestImport_Enum> => {
-        let value: Option<Types.TestImport_Enum>;
+      reader.context().push(field, "Array<Box<Types.TestImport_Enum> | null> | null", "type found, reading property");
+      _optEnumArray = reader.readOptionalArray((reader: Read): Box<Types.TestImport_Enum> | null => {
+        let value: Box<Types.TestImport_Enum> | null;
         if (!reader.isNextNil()) {
           if (reader.isNextString()) {
-            value = Option.Some(
+            value = Box.from(
               Types.getTestImport_EnumValue(reader.readString())
             );
           } else {
-            value = Option.Some(
+            value = Box.from(
               reader.readInt32()
             );
             Types.sanitizeTestImport_EnumValue(value.unwrap());
           }
         } else {
-          value = Option.None<Types.TestImport_Enum>();
+          value = null;
         }
         return value;
       });
diff --git a/packages/test-cases/cases/wrappers/wasm-as/reserved-words/src/index.ts b/packages/test-cases/cases/wrappers/wasm-as/reserved-words/src/index.ts
index 6ea15ddd4b..dd620c6443 100644
--- a/packages/test-cases/cases/wrappers/wasm-as/reserved-words/src/index.ts
+++ b/packages/test-cases/cases/wrappers/wasm-as/reserved-words/src/index.ts
@@ -3,7 +3,7 @@ import {
   Args__for,
   _else,
   _while,
-  Box,
+  _Box,
   getwhileKey
 } from "./wrap";
 
@@ -13,7 +13,7 @@ export function _if(args: Args__if): _else {
   };
 }
 
-export function _for(args: Args__for): Box {
+export function _for(args: Args__for): _Box {
   const value: _while = args._in;
   return {
     box: getwhileKey(value)
diff --git a/packages/wasm/as/assembly/__tests__/msgpack.spec.ts b/packages/wasm/as/assembly/__tests__/msgpack.spec.ts
index b464b41c99..76abba7f2c 100644
--- a/packages/wasm/as/assembly/__tests__/msgpack.spec.ts
+++ b/packages/wasm/as/assembly/__tests__/msgpack.spec.ts
@@ -6,11 +6,11 @@ import {
   Write,
   WriteEncoder,
   WriteSizer,
+  Box,
   JSON,
   BigInt,
   BigNumber,
 } from "../";
-import { Option } from "as-container";
 
 class Sanity {
   nil: string | null = "null";
@@ -21,8 +21,8 @@ class Sanity {
   uint16: u16;
   uint32: u32;
   boolean: bool;
-  optUint32: Option<u32> = Option.None<u32>();
-  optBool: Option<bool> = Option.None<bool>();
+  optUint32: Box<u32> | null = null;
+  optBool: Box<bool> | null = null;
   float32: f32;
   float64: f64;
   str: string = "";
@@ -49,8 +49,8 @@ class Sanity {
     this.uint16 = 65535;
     this.uint32 = 4294967295;
     this.boolean = true;
-    this.optUint32 = Option.Some<u32>(234234234);
-    this.optBool = Option.Some<bool>(true);
+    this.optUint32 = Box.from(<u32>234234234);
+    this.optBool = Box.from(true);
     this.float32 = 3.40282344818115234375;
     this.float64 = 3124124512.598273468017578125;
     this.str = "Hello, world!";
diff --git a/packages/wasm/as/assembly/__tests__/msgpack_write_option.spec.ts b/packages/wasm/as/assembly/__tests__/msgpack_write_optional.spec.ts
similarity index 91%
rename from packages/wasm/as/assembly/__tests__/msgpack_write_option.spec.ts
rename to packages/wasm/as/assembly/__tests__/msgpack_write_optional.spec.ts
index 58ac494560..a866476f93 100644
--- a/packages/wasm/as/assembly/__tests__/msgpack_write_option.spec.ts
+++ b/packages/wasm/as/assembly/__tests__/msgpack_write_optional.spec.ts
@@ -3,7 +3,7 @@ import { WriteSizer } from "../msgpack/WriteSizer";
 import { WriteEncoder } from "../msgpack/WriteEncoder";
 import { BigInt, BigNumber } from "../math";
 import { JSON } from "../json";
-import { Option } from "../";
+import { Box } from "../containers";
 
 function fill(arr: Array<u8>): ArrayBuffer {
   const buffer = new ArrayBuffer(arr.length);
@@ -26,12 +26,12 @@ class Case<T> {
   }
 }
 
-describe("WriteEncoder Option types", () => {
+describe("WriteEncoder optional types", () => {
   it("TestWriteOptionalBool", () => {
     const cases = [
-      new Case<Option<bool>>("nil", Option.None<bool>(), [192]),
-      new Case<Option<bool>>("nil", Option.Some(false), [194]),
-      new Case<Option<bool>>("nil", Option.Some(true), [195]),
+      new Case<Box<bool> | null>("nil", null, [192]),
+      new Case<Box<bool> | null>("nil", Box.from(false), [194]),
+      new Case<Box<bool> | null>("nil", Box.from(true), [195]),
     ];
 
     for (let i: i32 = 0; i < cases.length; ++i) {
@@ -50,10 +50,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalInt8", () => {
     const cases = [
-      new Case<Option<i8>>("none", Option.None<i8>(), [192]),
-      new Case<Option<i8>>(
+      new Case<Box<i8> | null>("none", null, [192]),
+      new Case<Box<i8> | null>(
         "positive fixed int",
-        Option.Some(<i8>-128),
+        Box.from(<i8>-128),
         [208,128]
       ),
     ];
@@ -74,10 +74,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalInt16", () => {
     const cases = [
-      new Case<Option<i16>>("none", Option.None<i16>(), [192]),
-      new Case<Option<i16>>(
+      new Case<Box<i16> | null>("none", null, [192]),
+      new Case<Box<i16> | null>(
         "16-bit signed int (negative)",
-        Option.Some(<i16>-32768),
+        Box.from(<i16>-32768),
         [209, 128, 0]
       ),
     ];
@@ -98,10 +98,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalInt32", () => {
     const cases = [
-      new Case<Option<i32>>("none", Option.None<i32>(), [192]),
-      new Case<Option<i32>>(
+      new Case<Box<i32> | null>("none", null, [192]),
+      new Case<Box<i32> | null>(
         "32-bit signed int (negative)",
-        Option.Some(-32769),
+        Box.from(-32769),
         [210, 255, 255, 127, 255]
       ),
     ];
@@ -122,10 +122,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalUint8", () => {
     const cases = [
-      new Case<Option<u8>>("none", Option.None<u8>(), [192]),
-      new Case<Option<u8>>(
+      new Case<Box<u8> | null>("none", null, [192]),
+      new Case<Box<u8> | null>(
         "8-bit unsigned int",
-        Option.Some(<u8>200),
+        Box.from(<u8>200),
         [204,200]
       ),
     ];
@@ -146,10 +146,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalUint16", () => {
     const cases = [
-      new Case<Option<u16>>("none", Option.None<u16>(), [192]),
-      new Case<Option<u16>>(
+      new Case<Box<u16> | null>("none", null, [192]),
+      new Case<Box<u16> | null>(
         "16-bit unsigned int",
-        Option.Some(<u16>256),
+        Box.from(<u16>256),
         [205,1,0]
       ),
     ];
@@ -170,10 +170,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalUint32", () => {
     const cases = [
-      new Case<Option<u32>>("none", Option.None<u32>(), [192]),
-      new Case<Option<u32>>(
+      new Case<Box<u32> | null>("none", null, [192]),
+      new Case<Box<u32> | null>(
         "32-bit unsigned int",
-        Option.Some(<u32>65536),
+        Box.from(<u32>65536),
         [206,0,1,0,0]
       ),
     ];
@@ -194,10 +194,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalFloat32", () => {
     const cases = [
-      new Case<Option<f32>>("none", Option.None<f32>(), [192]),
-      new Case<Option<f32>>(
+      new Case<Box<f32> | null>("none", null, [192]),
+      new Case<Box<f32> | null>(
         "32-bit float",
-        Option.Some(<f32>0.5),
+        Box.from(<f32>0.5),
         [202,63,0,0,0]
       ),
     ];
@@ -218,10 +218,10 @@ describe("WriteEncoder Option types", () => {
 
   it("TestWriteOptionalFloat64", () => {
     const cases = [
-      new Case<Option<f64>>("none", Option.None<f64>(), [192]),
-      new Case<Option<f64>>(
+      new Case<Box<f64> | null>("none", null, [192]),
+      new Case<Box<f64> | null>(
         "64-bit float",
-        Option.Some(<f64>3.141592653589793),
+        Box.from(<f64>3.141592653589793),
         [203, 64, 9, 33, 251, 84, 68, 45, 24]
       ),
     ];
diff --git a/packages/wasm/as/assembly/containers/index.ts b/packages/wasm/as/assembly/containers/index.ts
index 24b9e120e7..219d8c2dff 100644
--- a/packages/wasm/as/assembly/containers/index.ts
+++ b/packages/wasm/as/assembly/containers/index.ts
@@ -1 +1,2 @@
 export * from "./Result";
+export { Box } from "as-container";
diff --git a/packages/wasm/as/assembly/index.ts b/packages/wasm/as/assembly/index.ts
index 372b974bd4..38900a8a8d 100644
--- a/packages/wasm/as/assembly/index.ts
+++ b/packages/wasm/as/assembly/index.ts
@@ -1,4 +1,3 @@
-export { Option } from "as-container";
 export { Read, ReadDecoder, Write, WriteEncoder, WriteSizer } from "./msgpack";
 export * from "./json";
 export * from "./math";
diff --git a/packages/wasm/as/assembly/msgpack/Read.ts b/packages/wasm/as/assembly/msgpack/Read.ts
index 6237209a0e..1d3fd77a0f 100644
--- a/packages/wasm/as/assembly/msgpack/Read.ts
+++ b/packages/wasm/as/assembly/msgpack/Read.ts
@@ -1,8 +1,7 @@
 import { BigInt, BigNumber } from "../math";
 import { Context } from "../debug";
 import { JSON } from "../json";
-
-import { Option } from "as-container";
+import { Box } from "../containers";
 
 export abstract class Read {
   abstract readBool(): bool;
@@ -33,15 +32,15 @@ export abstract class Read {
     value_fn: (reader: Read) => V
   ): Map<K, V>;
 
-  abstract readOptionalBool(): Option<bool>;
-  abstract readOptionalInt8(): Option<i8>;
-  abstract readOptionalInt16(): Option<i16>;
-  abstract readOptionalInt32(): Option<i32>;
-  abstract readOptionalUInt8(): Option<u8>;
-  abstract readOptionalUInt16(): Option<u16>;
-  abstract readOptionalUInt32(): Option<u32>;
-  abstract readOptionalFloat32(): Option<f32>;
-  abstract readOptionalFloat64(): Option<f64>;
+  abstract readOptionalBool(): Box<bool> | null;
+  abstract readOptionalInt8(): Box<i8> | null;
+  abstract readOptionalInt16(): Box<i16> | null;
+  abstract readOptionalInt32(): Box<i32> | null;
+  abstract readOptionalUInt8(): Box<u8> | null;
+  abstract readOptionalUInt16(): Box<u16> | null;
+  abstract readOptionalUInt32(): Box<u32> | null;
+  abstract readOptionalFloat32(): Box<f32> | null;
+  abstract readOptionalFloat64(): Box<f64> | null;
   abstract readOptionalString(): string | null;
   abstract readOptionalBytes(): ArrayBuffer | null;
   abstract readOptionalBigInt(): BigInt | null;
diff --git a/packages/wasm/as/assembly/msgpack/ReadDecoder.ts b/packages/wasm/as/assembly/msgpack/ReadDecoder.ts
index 05c4dd4473..58a3529d1d 100644
--- a/packages/wasm/as/assembly/msgpack/ReadDecoder.ts
+++ b/packages/wasm/as/assembly/msgpack/ReadDecoder.ts
@@ -14,8 +14,7 @@ import { BigInt, BigNumber } from "../math";
 import { Context } from "../debug";
 import { JSON } from "../json";
 import { ExtensionType } from "./ExtensionType";
-
-import { Option } from "as-container";
+import { Box } from "../containers";
 
 export class ReadDecoder extends Read {
   private readonly _context: Context;
@@ -364,67 +363,67 @@ export class ReadDecoder extends Read {
     return this.readMap(key_fn, value_fn);
   }
 
-  readOptionalBool(): Option<bool> {
+  readOptionalBool(): Box<bool> | null {
     if (this.isNextNil()) {
-      return Option.None<bool>();
+      return null;
     }
-    return Option.Some<bool>(this.readBool());
+    return Box.from(this.readBool());
   }
 
-  readOptionalInt8(): Option<i8> {
+  readOptionalInt8(): Box<i8> | null {
     if (this.isNextNil()) {
-      return Option.None<i8>();
+      return null;
     }
-    return Option.Some<i8>(this.readInt8());
+    return Box.from(this.readInt8());
   }
 
-  readOptionalInt16(): Option<i16> {
+  readOptionalInt16(): Box<i16> | null {
     if (this.isNextNil()) {
-      return Option.None<i16>();
+      return null;
     }
-    return Option.Some<i16>(this.readInt16());
+    return Box.from(this.readInt16());
   }
 
-  readOptionalInt32(): Option<i32> {
+  readOptionalInt32(): Box<i32> | null {
     if (this.isNextNil()) {
-      return Option.None<i32>();
+      return null;
     }
-    return Option.Some<i32>(this.readInt32());
+    return Box.from(this.readInt32());
   }
 
-  readOptionalUInt8(): Option<u8> {
+  readOptionalUInt8(): Box<u8> | null {
     if (this.isNextNil()) {
-      return Option.None<u8>();
+      return null;
     }
-    return Option.Some<u8>(this.readUInt8());
+    return Box.from(this.readUInt8());
   }
 
-  readOptionalUInt16(): Option<u16> {
+  readOptionalUInt16(): Box<u16> | null {
     if (this.isNextNil()) {
-      return Option.None<u16>();
+      return null;
     }
-    return Option.Some<u16>(this.readUInt16());
+    return Box.from(this.readUInt16());
   }
 
-  readOptionalUInt32(): Option<u32> {
+  readOptionalUInt32(): Box<u32> | null {
     if (this.isNextNil()) {
-      return Option.None<u32>();
+      return null;
     }
-    return Option.Some<u32>(this.readUInt32());
+    return Box.from(this.readUInt32());
   }
 
-  readOptionalFloat32(): Option<f32> {
+  readOptionalFloat32(): Box<f32> | null {
     if (this.isNextNil()) {
-      return Option.None<f32>();
+      return null;
     }
-    return Option.Some<f32>(this.readFloat32());
+    return Box.from(this.readFloat32());
   }
 
-  readOptionalFloat64(): Option<f64> {
+  readOptionalFloat64(): Box<f64> | null {
     if (this.isNextNil()) {
-      return Option.None<f64>();
+      return null;
     }
-    return Option.Some<f64>(this.readFloat64());
+    return Box.from(this.readFloat64());
   }
 
   readOptionalString(): string | null {
diff --git a/packages/wasm/as/assembly/msgpack/Write.ts b/packages/wasm/as/assembly/msgpack/Write.ts
index 843a2ead8b..7f6e07d37d 100644
--- a/packages/wasm/as/assembly/msgpack/Write.ts
+++ b/packages/wasm/as/assembly/msgpack/Write.ts
@@ -1,8 +1,7 @@
 import { BigInt, BigNumber } from "../math";
 import { Context } from "../debug";
 import { JSON } from "../json";
-
-import { Option } from "as-container";
+import { Box } from "../containers";
 
 export abstract class Write {
   abstract writeNil(): void;
@@ -39,15 +38,15 @@ export abstract class Write {
     value_fn: (writer: Write, value: V) => void
   ): void;
 
-  abstract writeOptionalBool(value: Option<bool>): void;
-  abstract writeOptionalInt8(value: Option<i8>): void;
-  abstract writeOptionalInt16(value: Option<i16>): void;
-  abstract writeOptionalInt32(value: Option<i32>): void;
-  abstract writeOptionalUInt8(value: Option<u8>): void;
-  abstract writeOptionalUInt16(value: Option<u16>): void;
-  abstract writeOptionalUInt32(value: Option<u32>): void;
-  abstract writeOptionalFloat32(value: Option<f32>): void;
-  abstract writeOptionalFloat64(value: Option<f64>): void;
+  abstract writeOptionalBool(value: Box<bool> | null): void;
+  abstract writeOptionalInt8(value: Box<i8> | null): void;
+  abstract writeOptionalInt16(value: Box<i16> | null): void;
+  abstract writeOptionalInt32(value: Box<i32> | null): void;
+  abstract writeOptionalUInt8(value: Box<u8> | null): void;
+  abstract writeOptionalUInt16(value: Box<u16> | null): void;
+  abstract writeOptionalUInt32(value: Box<u32> | null): void;
+  abstract writeOptionalFloat32(value: Box<f32> | null): void;
+  abstract writeOptionalFloat64(value: Box<f64> | null): void;
   abstract writeOptionalString(value: string | null): void;
   abstract writeOptionalBytes(value: ArrayBuffer | null): void;
   abstract writeOptionalBigInt(value: BigInt | null): void;
diff --git a/packages/wasm/as/assembly/msgpack/WriteEncoder.ts b/packages/wasm/as/assembly/msgpack/WriteEncoder.ts
index 0894adefa9..abd58d6bcb 100644
--- a/packages/wasm/as/assembly/msgpack/WriteEncoder.ts
+++ b/packages/wasm/as/assembly/msgpack/WriteEncoder.ts
@@ -6,8 +6,7 @@ import { Write } from "./Write";
 import { BigInt, BigNumber } from "../math";
 import { Context } from "../debug";
 import { JSON } from "../json";
-
-import { Option } from "as-container";
+import { Box } from "../containers";
 
 export class WriteEncoder extends Write {
   private readonly _context: Context;
@@ -240,8 +239,8 @@ export class WriteEncoder extends Write {
     this.writeMap(m, key_fn, value_fn);
   }
 
-  writeOptionalBool(value: Option<bool>): void {
-    if (value.isNone) {
+  writeOptionalBool(value: Box<bool> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -249,8 +248,8 @@ export class WriteEncoder extends Write {
     this.writeBool(value.unwrap());
   }
 
-  writeOptionalInt8(value: Option<i8>): void {
-    if (value.isNone) {
+  writeOptionalInt8(value: Box<i8> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -258,8 +257,8 @@ export class WriteEncoder extends Write {
     this.writeInt8(value.unwrap());
   }
 
-  writeOptionalInt16(value: Option<i16>): void {
-    if (value.isNone) {
+  writeOptionalInt16(value: Box<i16> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -267,8 +266,8 @@ export class WriteEncoder extends Write {
     this.writeInt16(value.unwrap());
   }
 
-  writeOptionalInt32(value: Option<i32>): void {
-    if (value.isNone) {
+  writeOptionalInt32(value: Box<i32> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -276,8 +275,8 @@ export class WriteEncoder extends Write {
     this.writeInt32(value.unwrap());
   }
 
-  writeOptionalUInt8(value: Option<u8>): void {
-    if (value.isNone) {
+  writeOptionalUInt8(value: Box<u8> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -285,8 +284,8 @@ export class WriteEncoder extends Write {
     this.writeUInt8(value.unwrap());
   }
 
-  writeOptionalUInt16(value: Option<u16>): void {
-    if (value.isNone) {
+  writeOptionalUInt16(value: Box<u16> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -294,8 +293,8 @@ export class WriteEncoder extends Write {
     this.writeUInt16(value.unwrap());
   }
 
-  writeOptionalUInt32(value: Option<u32>): void {
-    if (value.isNone) {
+  writeOptionalUInt32(value: Box<u32> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -303,8 +302,8 @@ export class WriteEncoder extends Write {
     this.writeUInt32(value.unwrap());
   }
 
-  writeOptionalFloat32(value: Option<f32>): void {
-    if (value.isNone) {
+  writeOptionalFloat32(value: Box<f32> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -312,8 +311,8 @@ export class WriteEncoder extends Write {
     this.writeFloat32(value.unwrap());
   }
 
-  writeOptionalFloat64(value: Option<f64>): void {
-    if (value.isNone) {
+  writeOptionalFloat64(value: Box<f64> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
diff --git a/packages/wasm/as/assembly/msgpack/WriteSizer.ts b/packages/wasm/as/assembly/msgpack/WriteSizer.ts
index a02eb4b8f1..07f2f8fd9e 100644
--- a/packages/wasm/as/assembly/msgpack/WriteSizer.ts
+++ b/packages/wasm/as/assembly/msgpack/WriteSizer.ts
@@ -2,8 +2,7 @@ import { Write } from "./Write";
 import { BigInt, BigNumber } from "../math";
 import { Context } from "../debug";
 import { JSON } from "../json";
-
-import { Option } from "as-container";
+import { Box } from "../containers";
 
 export class WriteSizer extends Write {
   length: i32;
@@ -199,8 +198,8 @@ export class WriteSizer extends Write {
     this.extByteLengths[extIdx] = byteLength;
   }
 
-  writeOptionalBool(value: Option<bool>): void {
-    if (value.isNone) {
+  writeOptionalBool(value: Box<bool> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -208,8 +207,8 @@ export class WriteSizer extends Write {
     this.writeBool(value.unwrap());
   }
 
-  writeOptionalInt8(value: Option<i8>): void {
-    if (value.isNone) {
+  writeOptionalInt8(value: Box<i8> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -217,8 +216,8 @@ export class WriteSizer extends Write {
     this.writeInt8(value.unwrap());
   }
 
-  writeOptionalInt16(value: Option<i16>): void {
-    if (value.isNone) {
+  writeOptionalInt16(value: Box<i16> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -226,8 +225,8 @@ export class WriteSizer extends Write {
     this.writeInt16(value.unwrap());
   }
 
-  writeOptionalInt32(value: Option<i32>): void {
-    if (value.isNone) {
+  writeOptionalInt32(value: Box<i32> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -235,8 +234,8 @@ export class WriteSizer extends Write {
     this.writeInt32(value.unwrap());
   }
 
-  writeOptionalUInt8(value: Option<u8>): void {
-    if (value.isNone) {
+  writeOptionalUInt8(value: Box<u8> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -244,8 +243,8 @@ export class WriteSizer extends Write {
     this.writeUInt8(value.unwrap());
   }
 
-  writeOptionalUInt16(value: Option<u16>): void {
-    if (value.isNone) {
+  writeOptionalUInt16(value: Box<u16> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -253,8 +252,8 @@ export class WriteSizer extends Write {
     this.writeUInt16(value.unwrap());
   }
 
-  writeOptionalUInt32(value: Option<u32>): void {
-    if (value.isNone) {
+  writeOptionalUInt32(value: Box<u32> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -262,8 +261,8 @@ export class WriteSizer extends Write {
     this.writeUInt32(value.unwrap());
   }
 
-  writeOptionalFloat32(value: Option<f32>): void {
-    if (value.isNone) {
+  writeOptionalFloat32(value: Box<f32> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }
@@ -271,8 +270,8 @@ export class WriteSizer extends Write {
     this.writeFloat32(value.unwrap());
   }
 
-  writeOptionalFloat64(value: Option<f64>): void {
-    if (value.isNone) {
+  writeOptionalFloat64(value: Box<f64> | null): void {
+    if (value === null) {
       this.writeNil();
       return;
     }