--- a/mail/moz.configure
+++ b/mail/moz.configure
@@ -3,20 +3,21 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 imply_option('MOZ_PLACES', True)
 
 
 @depends(application)
-def is_comm(app):
-    return app[0].startswith('comm/')
+def is_comm_topdir(app):
+    return not app[0].startswith('comm/')
 
+set_config('MOZ_IS_COMM_TOPDIR', is_comm_topdir)
 
-@depends(is_comm)
-def toolkit_configure(is_comm):
-    if is_comm:
+@depends(is_comm_topdir)
+def toolkit_configure(is_comm_topdir):
+    if is_comm_topdir:
+        return '../mozilla/toolkit/moz.configure'
+    else:
         return '../../toolkit/moz.configure'
-    else:
-        return '../mozilla/toolkit/moz.configure'
 
 include(toolkit_configure)