diff --git a/stdlib/3/builtins.pyi b/stdlib/3/builtins.pyi
index 72270ac2f..9668245e9 100644
--- a/stdlib/3/builtins.pyi
+++ b/stdlib/3/builtins.pyi
@@ -382,7 +382,7 @@ class str(Sequence[str]):
     def maketrans(__x: str, __y: str, __z: Optional[str] = ...) -> Dict[int, Union[int, None]]: ...
     def __add__(self, s: str) -> str: ...
     # Incompatible with Sequence.__contains__
-    def __contains__(self, o: Union[str, str]) -> bool: ...  # type: ignore
+    def __contains__(self, o: str) -> bool: ...  # type: ignore
     def __eq__(self, x: object) -> bool: ...
     def __ge__(self, x: str) -> bool: ...
     def __getitem__(self, i: Union[int, slice]) -> str: ...