diff --git a/boards/views.py b/boards/views.py
--- a/boards/views.py
+++ b/boards/views.py
@@ -418,7 +418,7 @@ def api_get_post(request, post_id):
 def api_get_threaddiff(request, thread_id, last_update_time):
     """Get posts that were changed or added since time"""
 
-    thread = get_object_or_404(Post, id=thread_id)
+    thread = get_object_or_404(Post, id=thread_id).thread_new
 
     filter_time = datetime.fromtimestamp(float(last_update_time) / 1000000,
                                          timezone.get_current_timezone())
@@ -428,10 +428,10 @@ def api_get_threaddiff(request, thread_i
         'updated': [],
         'last_update': None,
     }
-    added_posts = Post.objects.filter(thread=thread,
+    added_posts = Post.objects.filter(thread_new=thread,
                                       pub_time__gt=filter_time)\
         .order_by('pub_time')
-    updated_posts = Post.objects.filter(thread=thread,
+    updated_posts = Post.objects.filter(thread_new=thread,
                                         pub_time__lte=filter_time,
                                         last_edit_time__gt=filter_time)
     for post in added_posts: