diff --git a/pflaenzli/pflaenzli/models.py b/pflaenzli/pflaenzli/models.py
index 1923aea..b9ba3df 100644
--- a/pflaenzli/pflaenzli/models.py
+++ b/pflaenzli/pflaenzli/models.py
@@ -52,9 +52,12 @@ def auto_delete_image_on_delete(sender, instance, **kwargs):
 
 @receiver(models.signals.pre_save, sender=Offer)
 def delete_old_image(sender, instance, **kwargs):
-    try:
-        old_image = sender.objects.get(pk=instance.pk).image
-    except sender.DoesNotExist:
-        return False
+    if instance.pk:
+        try:
+            old_image = sender.objects.get(pk=instance.pk).image
+        except sender.DoesNotExist:
+            return False
 
-    default_storage.delete(old_image.path)
+        new_image = instance.image
+        if old_image != new_image:
+            default_storage.delete(old_image.path)