diff --git a/testslide/mock_callable.py b/testslide/mock_callable.py
index e78aa482..743ab6e3 100644
--- a/testslide/mock_callable.py
+++ b/testslide/mock_callable.py
@@ -597,7 +597,12 @@ def _validate_patch(
                     )
                 if (
                     coroutine_function
-                    and not inspect.iscoroutinefunction(template_value)
+                    and (
+                        # FIXME We cant reliably introspect coroutine functions
+                        # for builtins: https://bugs.python.org/issue38225
+                        type(template_value) is not type(list.append)
+                        and not inspect.iscoroutinefunction(template_value)
+                    )
                     and not callable_returns_coroutine
                 ):
                     raise ValueError(
@@ -640,7 +645,12 @@ def _validate_patch(
                 )
             if (
                 coroutine_function
-                and not inspect.iscoroutinefunction(original_callable)
+                and (
+                    # FIXME We cant reliably introspect coroutine functions
+                    # for builtins: https://bugs.python.org/issue38225
+                    type(original_callable) is not type(list.append)
+                    and not inspect.iscoroutinefunction(original_callable)
+                )
                 and not callable_returns_coroutine
             ):
                 raise ValueError(