diff --git a/src/Monitoring/Unread.coffee b/src/Monitoring/Unread.coffee
index 2934fce49..80a296297 100755
--- a/src/Monitoring/Unread.coffee
+++ b/src/Monitoring/Unread.coffee
@@ -154,6 +154,10 @@ Unread =
     Unread.update()
 
   read: $.debounce 100, (e) ->
+    # Update the lastReadPost when hidden posts are added to the thread.
+    if !Unread.posts.size and Unread.readCount isnt Unread.thread.posts.keys.length
+      Unread.saveLastReadPost()
+
     return if d.hidden or !Unread.posts.size
     height  = doc.clientHeight