diff --git a/third_party/2/gflags.pyi b/third_party/2/gflags.pyi
index a3daaa982..0c8c03de4 100644
--- a/third_party/2/gflags.pyi
+++ b/third_party/2/gflags.pyi
@@ -60,7 +60,7 @@ class FlagValues:
     def __contains__(self, name: str) -> bool: ...
     has_key = __contains__
     def __iter__(self) -> Iterable[str]: ...
-    def __call__(self, argv: List[str]) -> List[str]: ...
+    def __call__(self, argv: List[str], known_only: bool = ...) -> List[str]: ...
     def reset(self) -> None: ...
     Reset = reset
     def RegisteredFlags(self) -> List[str]: ...