diff --git a/serializable/__init__.py b/serializable/__init__.py
index 1ed02c2..e89e3e7 100644
--- a/serializable/__init__.py
+++ b/serializable/__init__.py
@@ -1130,7 +1130,7 @@ def register_property_type_mapping(cls, qual_name: str, mapped_type: type) -> No
 
 
 @overload
-def serializable_enum(cls: 'Literal[None]' = None) -> Callable[[Type[_E]], Type[_E]]:
+def serializable_enum(cls: Literal[None] = None) -> Callable[[Type[_E]], Type[_E]]:
     ...
 
 
@@ -1160,7 +1160,7 @@ def decorate(kls: Type[_E]) -> Type[_E]:
 
 @overload
 def serializable_class(
-        cls: 'Literal[None]' = None, *,
+        cls: Literal[None] = None, *,
         name: Optional[str] = ...,
         serialization_types: Optional[Iterable[SerializationType]] = ...,
         ignore_during_deserialization: Optional[Iterable[str]] = ...