diff --git a/stdlib/dbm/__init__.pyi b/stdlib/dbm/__init__.pyi
index 0068d67b6..d71155288 100644
--- a/stdlib/dbm/__init__.pyi
+++ b/stdlib/dbm/__init__.pyi
@@ -90,5 +90,5 @@ class _error(Exception): ...
 
 error: tuple[type[_error], type[OSError]]
 
-def whichdb(filename: str) -> str: ...
+def whichdb(filename: str) -> str | None: ...
 def open(file: str, flag: _TFlags = "r", mode: int = 0o666) -> _Database: ...