diff --git a/include/class.thread.php b/include/class.thread.php
index 34c5e14a694603d859e82ba9f9eb4f165343f832..c4255ac7c27cd76d03d0d73f37731da7f692e116 100644
--- a/include/class.thread.php
+++ b/include/class.thread.php
@@ -728,7 +728,7 @@ Class ThreadEntry {
         $subject = $mailinfo['subject'];
         $match = array();
         if ($subject && $mailinfo['email']
-                && preg_match("/#[\p{L}-]+?([0-9]{1,10})/u", $subject, $match)
+                && preg_match("/#(?:[\p{L}-]+)?([0-9]{1,10})/u", $subject, $match)
                 && ($tid = Ticket::getIdByExtId((int)$match[1], $mailinfo['email']))
                 )
             // Return last message for the thread