diff --git a/src/tests/Loader/classloader/generics/ByRefLike/Validate.csproj b/src/tests/Loader/classloader/generics/ByRefLike/Validate.csproj
index a1b5c8740e939e..a58570306baff8 100644
--- a/src/tests/Loader/classloader/generics/ByRefLike/Validate.csproj
+++ b/src/tests/Loader/classloader/generics/ByRefLike/Validate.csproj
@@ -2,6 +2,10 @@
   <PropertyGroup>
     <!-- https://github.com/dotnet/runtime/issues/90427  -->
     <MonoAotIncompatible>true</MonoAotIncompatible>
+    <!-- Needed for MonoAotIncompatible: keeps this project out of the merged test runner so the
+         MonoAotIncompatible exclusion of InvalidCSharp.ilproj under minifullaot/llvmfullaot does not
+         leave this source referencing a type that was not built. Mirrors ValidateNegative.csproj. -->
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Validate.cs" />