diff --git a/src/Monitoring/MarkNewIPs.coffee b/src/Monitoring/MarkNewIPs.coffee
index 263d7e53a..456658c89 100644
--- a/src/Monitoring/MarkNewIPs.coffee
+++ b/src/Monitoring/MarkNewIPs.coffee
@@ -7,29 +7,21 @@ MarkNewIPs =
 
   node: ->
     MarkNewIPs.ipCount = @ipCount
-    MarkNewIPs.postIDs = (+x for x in @posts.keys)
     $.on d, 'ThreadUpdate', MarkNewIPs.onUpdate
 
   onUpdate: (e) ->
-    {ipCount, newPosts} = e.detail
-    {postIDs} = ThreadUpdater
+    {ipCount, newPosts, deletedPosts} = e.detail
     return unless ipCount?
-    if newPosts.length
-      obj = {}
-      obj[x] = true for x in MarkNewIPs.postIDs
-      added = 0
-      added++ for x in postIDs when not (x of obj)
-      removed = MarkNewIPs.postIDs.length + added - postIDs.length
-      switch ipCount - MarkNewIPs.ipCount
-        when added
-          i = MarkNewIPs.ipCount
-          for fullID in newPosts
-            MarkNewIPs.markNew g.posts[fullID], ++i
-        when -removed
-          for fullID in newPosts
-            MarkNewIPs.markOld g.posts[fullID]
+
+    switch ipCount - MarkNewIPs.ipCount
+      when newPosts.length
+        i = MarkNewIPs.ipCount
+        for fullID in newPosts
+          MarkNewIPs.markNew g.posts[fullID], ++i
+      when -deletedPosts.length
+        for fullID in newPosts
+          MarkNewIPs.markOld g.posts[fullID]
     MarkNewIPs.ipCount = ipCount
-    MarkNewIPs.postIDs = postIDs
 
   markNew: (post, ipCount) ->
     suffix = if (ipCount // 10) % 10 is 1