diff --git a/plone/app/discussion/browser/comments.py b/plone/app/discussion/browser/comments.py
index 529df18..bcf5dbe 100644
--- a/plone/app/discussion/browser/comments.py
+++ b/plone/app/discussion/browser/comments.py
@@ -358,7 +358,10 @@ class CommentsViewlet(ViewletBase):
         returned with workflow actions.
         """
         context = aq_inner(self.context)
-        conversation = IConversation(context)
+        conversation = IConversation(context, None)
+
+        if conversation is None:
+            return iter([])
 
         wf = getToolByName(context, 'portal_workflow')
 
diff --git a/plone/app/discussion/tests/test_comments_viewlet.py b/plone/app/discussion/tests/test_comments_viewlet.py
index 1844b28..8b742c8 100644
--- a/plone/app/discussion/tests/test_comments_viewlet.py
+++ b/plone/app/discussion/tests/test_comments_viewlet.py
@@ -370,6 +370,14 @@ class TestCommentsViewlet(unittest.TestCase):
         replies.next()
         self.assertRaises(StopIteration, replies.next)
 
+    def test_get_replies_on_non_annotatable_object(self):
+        context = self.portal.MailHost      # the mail host is not annotatable
+        viewlet = CommentsViewlet(context, self.request, None, None)
+        replies = viewlet.get_replies()
+        self.assertEqual(len(tuple(replies)), 0)
+        replies = viewlet.get_replies()
+        self.assertRaises(StopIteration, replies.next)
+
     def test_get_replies_with_workflow_actions(self):
         self.assertFalse(self.viewlet.get_replies(workflow_actions=True))
         comment = createObject('plone.Comment')