diff --git a/stubs/Markdown/markdown/util.pyi b/stubs/Markdown/markdown/util.pyi
index 4142d6b0f..3af385c70 100644
--- a/stubs/Markdown/markdown/util.pyi
+++ b/stubs/Markdown/markdown/util.pyi
@@ -47,7 +47,7 @@ class Registry:
     def __getitem__(self, key: slice) -> Registry: ...
     @overload
     def __getitem__(self, key: str | int) -> Any: ...
-    def __len__(self): ...
+    def __len__(self) -> int: ...
     def get_index_for_name(self, name: str) -> int: ...
     def register(self, item: Any, name: str, priority: float) -> None: ...
     def deregister(self, name: str, strict: bool = ...) -> None: ...