diff --git a/stubs/Markdown/markdown/util.pyi b/stubs/Markdown/markdown/util.pyi
index a8fb724d2..437d63f17 100644
--- a/stubs/Markdown/markdown/util.pyi
+++ b/stubs/Markdown/markdown/util.pyi
@@ -16,7 +16,7 @@ INSTALLED_EXTENSIONS: Any
 RTL_BIDI_RANGES: Any
 
 def deprecated(message: str, stacklevel: int = ...): ...
-def isBlockLevel(tag): ...
+def isBlockLevel(tag: object) -> bool: ...
 def parseBoolValue(value, fail_on_errors: bool = ..., preserve_none: bool = ...): ...
 def code_escape(text): ...