diff --git a/stdlib/3/sys.pyi b/stdlib/3/sys.pyi
index f7afaeb55..b35f6d7a9 100644
--- a/stdlib/3/sys.pyi
+++ b/stdlib/3/sys.pyi
@@ -161,7 +161,7 @@ def setprofile(profilefunc: Optional[_ProfileFunc]) -> None: ...
 
 _TraceFunc = Callable[[FrameType, str, Any], Optional[Callable[[FrameType, str, Any], Any]]]
 def gettrace() -> Optional[_TraceFunc]: ...
-def settrace(tracefunc: _TraceFunc) -> None: ...
+def settrace(tracefunc: Optional[_TraceFunc]) -> None: ...
 
 
 class _WinVersion(Tuple[int, int, int, int,