diff --git a/stdlib/email/message.pyi b/stdlib/email/message.pyi
index fcf8d7969..9ad8c1852 100644
--- a/stdlib/email/message.pyi
+++ b/stdlib/email/message.pyi
@@ -28,6 +28,7 @@ class Message:
     def get_charset(self) -> _CharsetType: ...
     def __len__(self) -> int: ...
     def __contains__(self, name: str) -> bool: ...
+    def __iter__(self) -> Iterator[str]: ...
     def __getitem__(self, name: str) -> _HeaderType: ...
     def __setitem__(self, name: str, val: _HeaderType) -> None: ...
     def __delitem__(self, name: str) -> None: ...