diff --git a/flaschengeist/models/__init__.py b/flaschengeist/models/__init__.py
index 5f9484a..c7b94d1 100644
--- a/flaschengeist/models/__init__.py
+++ b/flaschengeist/models/__init__.py
@@ -15,10 +15,9 @@ class ModelSerializeMixin:
 
         import typing
 
-        if (
-            typing.get_origin(self.__class__.__annotations__[param]) is typing.Union
-            and isinstance(typing.get_args(self.__class__.__annotations__[param])[1], type(None))
-        ):
+        if typing.get_origin(self.__class__.__annotations__[param]) is typing.Union and typing.get_args(
+            self.__class__.__annotations__[param]
+        )[1] is type(None):
             return getattr(self, param) is None
 
     def serialize(self):