diff --git a/stdlib/3/types.pyi b/stdlib/3/types.pyi
index 634ac39b0..2c1c903d6 100644
--- a/stdlib/3/types.pyi
+++ b/stdlib/3/types.pyi
@@ -78,8 +78,10 @@ class MappingProxyType(Mapping[_KT, _VT], Generic[_KT, _VT]):
     def __iter__(self) -> Iterator[_KT]: ...
     def __len__(self) -> int: ...
 
-# TODO: use __getattr__ and __setattr__ instead of inheriting from Any, pending mypy#521.
-class SimpleNamespace(Any): ...  # type: ignore
+class SimpleNamespace:
+    def __getattribute__(self, name: str) -> Any: ...
+    def __setattr__(self, name: str, value: Any) -> None: ...
+    def __delattr__(self, name: str) -> None: ...
 
 class GeneratorType:
     gi_code = ...  # type: CodeType