diff --git a/flaschengeist/models/__init__.py b/flaschengeist/models/__init__.py
index c7b94d1..27431a0 100644
--- a/flaschengeist/models/__init__.py
+++ b/flaschengeist/models/__init__.py
@@ -14,10 +14,8 @@ class ModelSerializeMixin:
             return False
 
         import typing
-
-        if typing.get_origin(self.__class__.__annotations__[param]) is typing.Union and typing.get_args(
-            self.__class__.__annotations__[param]
-        )[1] is type(None):
+        hint = typing.get_type_hints(self.__class__)[param]
+        if typing.get_origin(hint) is typing.Union and len(typing.get_args(hint)) == 2 and typing.get_args(hint)[1] is type(None):
             return getattr(self, param) is None
 
     def serialize(self):
diff --git a/flaschengeist/plugins/schedule/models.py b/flaschengeist/plugins/schedule/models.py
index 04c060f..228ed0d 100644
--- a/flaschengeist/plugins/schedule/models.py
+++ b/flaschengeist/plugins/schedule/models.py
@@ -80,7 +80,7 @@ class Event(db.Model, ModelSerializeMixin):
 
     id: int = db.Column(db.Integer, primary_key=True)
     start: datetime = db.Column(UtcDateTime, nullable=False)
-    end: datetime = db.Column(UtcDateTime)
+    end: Optional[datetime] = db.Column(UtcDateTime)
     description: Optional[str] = db.Column(db.String(255))
     type: EventType = db.relationship("EventType")
     jobs: list[Job] = db.relationship(