diff --git a/mozilla/webtools/bugzilla/Bugzilla/BugMail.pm b/mozilla/webtools/bugzilla/Bugzilla/BugMail.pm
index 1085c8b9357..85393a74e89 100644
--- a/mozilla/webtools/bugzilla/Bugzilla/BugMail.pm
+++ b/mozilla/webtools/bugzilla/Bugzilla/BugMail.pm
@@ -645,7 +645,8 @@ sub sendMail {
         $threadingmarker = "Message-ID: <bug-$id-" . $user->id . "$sitespec>";
     }
     else {
-        $threadingmarker = "In-Reply-To: <bug-$id-" . $user->id . "$sitespec>";
+        $threadingmarker = "In-Reply-To: <bug-$id-" . $user->id . "$sitespec>" .
+                            "\nReferences: <bug-$id-" . $user->id . "$sitespec>";
     }