diff --git a/poetry/core/masonry/builders/sdist.py b/poetry/core/masonry/builders/sdist.py
index df07bb293..b653badbc 100644
--- a/poetry/core/masonry/builders/sdist.py
+++ b/poetry/core/masonry/builders/sdist.py
@@ -139,7 +139,14 @@ def build_setup(self) -> bytes:
                     pkg_dir, _packages, _package_data = self.find_packages(include)
 
                     if pkg_dir is not None:
-                        package_dir[""] = os.path.relpath(pkg_dir, str(self._path))
+                        pkg_root = os.path.relpath(pkg_dir, str(self._path))
+                        if "" in package_dir:
+                            package_dir.update(
+                                (p, os.path.join(pkg_root, p.replace(".", "/")))
+                                for p in _packages
+                            )
+                        else:
+                            package_dir[""] = pkg_root
 
                     packages += [p for p in _packages if p not in packages]
                     package_data.update(_package_data)
diff --git a/tests/masonry/builders/fixtures/split_source/lib_a/module_a/__init__.py b/tests/masonry/builders/fixtures/split_source/lib_a/module_a/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/masonry/builders/fixtures/split_source/lib_b/module_b/__init__.py b/tests/masonry/builders/fixtures/split_source/lib_b/module_b/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/masonry/builders/fixtures/split_source/pyproject.toml b/tests/masonry/builders/fixtures/split_source/pyproject.toml
new file mode 100644
index 000000000..f11bba047
--- /dev/null
+++ b/tests/masonry/builders/fixtures/split_source/pyproject.toml
@@ -0,0 +1,15 @@
+[tool.poetry]
+name = "split-source"
+version = "0.1"
+description = "Combine packages from different locations."
+authors = [
+    "Jan Harkes <jaharkes@cs.cmu.edu>"
+]
+license = "MIT"
+packages = [
+    { include = "module_a", from = "lib_a" },
+    { include = "module_b", from = "lib_b" },
+]
+
+[tool.poetry.dependencies]
+python = "^3.6"
diff --git a/tests/masonry/builders/test_sdist.py b/tests/masonry/builders/test_sdist.py
index ae299595a..7ccd65ee9 100644
--- a/tests/masonry/builders/test_sdist.py
+++ b/tests/masonry/builders/test_sdist.py
@@ -629,3 +629,19 @@ def test_sdist_mtime_zero():
     with gzip.open(str(sdist), "rb") as gz:
         gz.read(100)
         assert gz.mtime == 0
+
+
+def test_split_source():
+    root = fixtures_dir / "split_source"
+    poetry = Factory().create_poetry(root)
+
+    builder = SdistBuilder(poetry)
+
+    # Check setup.py
+    setup = builder.build_setup()
+    setup_ast = ast.parse(setup)
+
+    setup_ast.body = [n for n in setup_ast.body if isinstance(n, ast.Assign)]
+    ns = {}
+    exec(compile(setup_ast, filename="setup.py", mode="exec"), ns)
+    assert "" in ns["package_dir"] and "module_b" in ns["package_dir"]