diff --git a/cursed_snakes/namespace_inject.py b/cursed_snakes/namespace_inject.py
index 0a8044b..583406c 100644
--- a/cursed_snakes/namespace_inject.py
+++ b/cursed_snakes/namespace_inject.py
@@ -1,6 +1,5 @@
 import ast
 import inspect
-from textwrap import dedent
 from typing import Callable
 
 ##################
@@ -21,17 +20,22 @@ class namespace_inject:
         self.local_fns = local_fn
 
     @staticmethod
-    def _get_func_def(object: Callable) -> tuple[ast.Module, ast.FunctionDef]:
+    def _get_func_def(fn: Callable) -> tuple[ast.Module, ast.FunctionDef]:
         """
         Get the AST representation and the contained ast.FunctionDef
         of a function
         """
-        object_ast = ast.parse(dedent(inspect.getsource(object)))
+        assert (object_module := inspect.getmodule(fn)) is not None
+        module_ast = ast.parse(inspect.getsource(object_module))
 
-        return object_ast, next(
-            x for x in ast.walk(object_ast)
-            if isinstance(x, ast.FunctionDef) and x.name == object.__name__
-        )
+        function_defs = [
+            x for x in ast.walk(module_ast)
+            if isinstance(x, ast.FunctionDef) and x.name == fn.__name__
+        ]
+        assert len(function_defs) == 1, \
+            f"Function {fn.__name__} must have a unique name in its module!"
+
+        return module_ast, function_defs[0]
 
     def __call__(self, fn: Callable) -> Callable:
         """
@@ -71,7 +75,7 @@ class namespace_inject:
 
 
 def foo() -> None:
-    # foo, but in global namespace it uses an unbound variable
+    # foo in global namespace uses unbound variable `pstr`
 
     print(f"{pstr = }")  # type:ignore # noqa: F821
 
@@ -91,11 +95,13 @@ def call_foo_local(pstr: str) -> None:
     In local namespace, `pstr` is defined.
     """
 
-    def foo() -> None:
-        # foo in local namespace is fine
+    def foo_local() -> None:
+        # foo in local namespace is fine (same code as global foo)
 
         print(f"{pstr = }")
 
+    foo = foo_local
+
     foo()