diff --git a/app/models/topic.py b/app/models/topic.py
index 307b1fc..abc00bf 100644
--- a/app/models/topic.py
+++ b/app/models/topic.py
@@ -9,7 +9,6 @@ class Topic(Post):
 
     __mapper_args__ = {
       'polymorphic_identity': __tablename__,
-      'primary_key': id,
       'inherit_condition': id == Post.id
     }