diff --git a/django-stubs/forms/forms.pyi b/django-stubs/forms/forms.pyi
index 64eecf9..bb7be6b 100644
--- a/django-stubs/forms/forms.pyi
+++ b/django-stubs/forms/forms.pyi
@@ -24,7 +24,7 @@ class BaseForm:
     auto_id: Union[bool, str] = ...
     initial: Dict[str, Any] = ...
     error_class: Type[ErrorList] = ...
-    prefix: str = ...
+    prefix: Optional[str] = ...
     label_suffix: str = ...
     empty_permitted: bool = ...
     fields: Dict[str, Any] = ...