--- a/hghooks/mozhghooks/treeclosure_comm_central.py
+++ b/hghooks/mozhghooks/treeclosure_comm_central.py
@@ -20,16 +20,20 @@ from urllib2 import urlopen
 import os.path
 import re
 import json
 
 # Array of which directories SeaMonkey exclusively controls in comm-central
 seamonkeyOwns = [
   'suite'
 ]
+# Array of which directories Instantbird exclusively controls in comm-central
+instantbirdOwns = [
+  'im'
+]
 # Everything else is assumed to be controlled by Thunderbird.
 
 magicwords = "CLOSED TREE"
 
 treestatus_base_url = "https://treestatus.mozilla.org"
 
 def printError(message):
     print "\n\n************************** ERROR ****************************"
@@ -102,16 +106,18 @@ def hook(ui, repo, node, **kwargs):
         # all changesets from node to 'tip' inclusive are part of this push
         rev = repo.changectx(node).rev()
         tip = repo.changectx('tip').rev()
         for i in range(rev, tip+1):
             ctx = repo.changectx(i)
             for changedFile in ctx.files():
                 if isOwned(changedFile, seamonkeyOwns):
                     apps['seamonkey'] = True
+                elif isOwned(changedFile, instantbirdOwns):
+                    pass  # ignore Instantbird for tree closure reasons
                 else:
                     apps['thunderbird'] = True
 
         repoName = os.path.basename(repo.root)
         status = 0
 
         for app in apps:
             if apps[app]: