Ticket #13839: 13839_1.diff

django/db/models/fields/related.py

@@ -219 +219 @@
         if instance is None:
             return self
         try:
-            return getattr(instance, self.cache_name)
+            rel_obj = getattr(instance, self.cache_name)
+            if rel_obj is None:
+                rmod = self.related.model
+                raise rmod.DoesNotExist( 'related %s does not exist' % rmod.__name__ )
+            return rel_obj
         except AttributeError:
             params = {'%s__pk' % self.related.field.name: instance._get_pk_val()}
             db = router.db_for_read(self.related.model, instance=instance)