diff --git a/symposion/schedule/models.py b/symposion/schedule/models.py
index a47afb9d909a3f4d169a76f6ac7ca1c188b3d7b6..5954e07e861501611a4864a09557addbfd6f45a8 100644
--- a/symposion/schedule/models.py
+++ b/symposion/schedule/models.py
@@ -80,8 +80,9 @@ class Slot(models.Model):
         Unassign the associated content with this slot.
         """
         if self.content and self.content.slot_id:
-            self.content.slot = None
-            self.content.save()
+            presentation = self.content
+            presentation.slot = None
+            presentation.save()
 
     @property
     def content(self):