diff --git a/rhodecode/controllers/changeset.py b/rhodecode/controllers/changeset.py
--- a/rhodecode/controllers/changeset.py
+++ b/rhodecode/controllers/changeset.py
@@ -234,7 +234,7 @@ class ChangesetController(BaseRepoContro
                 # show comments from them
 
                 prs = set([x.pull_request for x in
-                           filter(lambda x: x.pull_request != None, st)])
+                           filter(lambda x: x.pull_request is not None, st)])
 
                 for pr in prs:
                     c.comments.extend(pr.comments)