diff --git a/extra_tests/snippets/builtin_type.py b/extra_tests/snippets/builtin_type.py
index 820ee366155..abb68f812be 100644
--- a/extra_tests/snippets/builtin_type.py
+++ b/extra_tests/snippets/builtin_type.py
@@ -1,6 +1,6 @@
 import types
-from testutils import assert_raises
 
+from testutils import assert_raises
 
 # Spec: https://docs.python.org/2/library/types.html
 print(None)
@@ -111,8 +111,6 @@ class D:
 with assert_raises(TypeError):
     del int.__qualname__
 
-from testutils import assert_raises
-
 import platform
 
 if platform.python_implementation() == "RustPython":
@@ -607,3 +605,24 @@ class A(type):
 
 
 assert "__dict__" not in A.__dict__
+
+
+# regression tests for: https://github.com/RustPython/RustPython/issues/4505
+
+
+def foo():
+    def inner():
+        pass
+
+
+assert foo.__code__.co_names == ()
+
+stmts = """
+import blah
+
+def foo():
+    pass
+"""
+
+code = compile(stmts, "<test>", "exec")
+assert code.co_names == ("blah", "foo")