diff --git a/boards/models/post/sync.py b/boards/models/post/sync.py
--- a/boards/models/post/sync.py
+++ b/boards/models/post/sync.py
@@ -196,7 +196,14 @@ class SyncManager:
         global_id, exists = GlobalId.from_xml_element(tag_id)
         signatures = SyncManager._verify_model(global_id, content_str, tag_model)
 
-        update_time = tag_content.find(TAG_UPDATE_TIME).text
+        pub_time = tag_content.find(TAG_PUB_TIME).text
+
+        tag_update_time = tag_content.find(TAG_UPDATE_TIME)
+        if tag_update_time:
+            update_time = tag_content.find(TAG_UPDATE_TIME).text
+        else:
+            update_time = pub_time
+
         is_old = exists and global_id.post.last_edit_time < parse_datetime(update_time)
         if exists and not is_old:
             logger.debug('Post {} exists and is up to date.'.format(global_id))
@@ -215,7 +222,6 @@ class SyncManager:
             else:
                 tripcode = ''
 
-            pub_time = tag_content.find(TAG_PUB_TIME).text
             thread = tag_content.find(TAG_THREAD)
             tags = []
             if thread: