Ticket #13137: allow_contenttype_id_0.patch

django/contrib/contenttypes/generic.py

@@ -51 +51 @@
         ContentType = get_model("contenttypes", "contenttype")
         if obj:
              return ContentType.objects.db_manager(obj._state.db).get_for_model(obj)
-        elif id:
+        elif id is not None:
              return ContentType.objects.db_manager(using).get_for_id(id)
         else:
             # This should never happen. I love comments like this, don't you?
@@ -72 +72 @@
             # performance when dealing with GFKs in loops and such.
             f = self.model._meta.get_field(self.ct_field)
             ct_id = getattr(instance, f.get_attname(), None)
-            if ct_id:
+            if ct_id is not None:
                 ct = self.get_content_type(id=ct_id, using=instance._state.db)
                 try:
                     rel_obj = ct.get_object_for_this_type(pk=getattr(instance, self.fk_field))