diff --git a/stdlib/2and3/contextlib.pyi b/stdlib/2and3/contextlib.pyi
index c7954ea37..3abaf61a8 100644
--- a/stdlib/2and3/contextlib.pyi
+++ b/stdlib/2and3/contextlib.pyi
@@ -68,7 +68,7 @@ if sys.version_info >= (3,):
 if sys.version_info >= (3, 7):
     from typing import Awaitable
 
-    _U = TypeVar('_U', bound='AsyncExitStack')
+    _S = TypeVar('_S', bound='AsyncExitStack')
 
     _ExitCoroFunc = Callable[[Optional[Type[BaseException]],
                               Optional[BaseException],
@@ -86,6 +86,6 @@ if sys.version_info >= (3, 7):
                      *args: Any, **kwds: Any) -> Callable[..., None]: ...
         def push_async_callback(self, callback: _CallbackCoroFunc,
                                 *args: Any, **kwds: Any) -> _CallbackCoroFunc: ...
-        def pop_all(self: _U) -> _U: ...
+        def pop_all(self: _S) -> _S: ...
         def aclose(self) -> Awaitable[None]: ...
-        def __aenter__(self: _U) -> Awaitable[_U]: ...
+        def __aenter__(self: _S) -> Awaitable[_S]: ...