diff --git a/django-stubs/forms/forms.pyi b/django-stubs/forms/forms.pyi
index bf9fe45..4a1c71f 100644
--- a/django-stubs/forms/forms.pyi
+++ b/django-stubs/forms/forms.pyi
@@ -21,7 +21,7 @@ class BaseForm:
     is_bound: bool = ...
     data: Dict[str, Any] = ...
     files: MultiValueDict[str, uploadedfile.UploadedFile] = ...
-    auto_id: str = ...
+    auto_id: Union[bool, str] = ...
     initial: Dict[str, Any] = ...
     error_class: Type[ErrorList] = ...
     prefix: str = ...