diff --git a/stubs/Markdown/markdown/core.pyi b/stubs/Markdown/markdown/core.pyi
index 3cfdb6761..96aa61a37 100644
--- a/stubs/Markdown/markdown/core.pyi
+++ b/stubs/Markdown/markdown/core.pyi
@@ -32,6 +32,7 @@ class Markdown:
     serializer: Callable[[Element], str]
     tab_length: int
     block_level_elements: list[str]
+    registeredExtensions: list[Extension]
     def __init__(
         self,
         *,