diff --git a/boards/views.py b/boards/views.py
--- a/boards/views.py
+++ b/boards/views.py
@@ -429,7 +429,7 @@ def api_get_threaddiff(request, thread_i
                                       pub_time__gt=filter_time)\
         .order_by('pub_time')
     updated_posts = Post.objects.filter(thread=thread,
-                                        pub_time__lt=filter_time,
+                                        pub_time__lte=filter_time,
                                         last_edit_time__gt=filter_time)
     for post in added_posts:
         json_data['added'].append(get_post(request, post.id).content.strip())
@@ -561,4 +561,4 @@ def _remove_invalid_links(text):
 def _datetime_to_epoch(datetime):
     return int(time.mktime(timezone.localtime(
         datetime,timezone.get_current_timezone()).timetuple())
-               * 1000000 + datetime.microsecond)
\ No newline at end of file
+               * 1000000 + datetime.microsecond)