diff --git a/stdlib/sys.pyi b/stdlib/sys.pyi
index a6e10affc..c437f3f66 100644
--- a/stdlib/sys.pyi
+++ b/stdlib/sys.pyi
@@ -317,6 +317,10 @@ class _asyncgen_hooks(structseq[_AsyncgenHook], tuple[_AsyncgenHook, _AsyncgenHo
 def get_asyncgen_hooks() -> _asyncgen_hooks: ...
 def set_asyncgen_hooks(firstiter: _AsyncgenHook = ..., finalizer: _AsyncgenHook = ...) -> None: ...
 
+if sys.version_info >= (3, 6):
+    if sys.platform == "win32":
+        def _enablelegacywindowsfsencoding() -> None: ...
+
 if sys.version_info >= (3, 7):
     def get_coroutine_origin_tracking_depth() -> int: ...
     def set_coroutine_origin_tracking_depth(depth: int) -> None: ...