diff --git a/core/__pycache__/models.cpython-311.pyc b/core/__pycache__/models.cpython-311.pyc
index 73573bf..25fd7c1 100644
Binary files a/core/__pycache__/models.cpython-311.pyc and b/core/__pycache__/models.cpython-311.pyc differ
diff --git a/core/models.py b/core/models.py
index d2892a0..a095a74 100644
--- a/core/models.py
+++ b/core/models.py
@@ -24,7 +24,7 @@ class Event(models.Model):
 
     def clean(self):
         super().clean()
-        if self.end <= self.start:
+        if self.start is not None and self.end is not None and self.end <= self.start:
             raise ValidationError({'end': 'End time must be after the start time.'})
 
     def save(self, *args, **kwargs):