diff --git a/app/models/observer/ticket/notification.rb b/app/models/observer/ticket/notification.rb
index 707f9b7ea..5da41d6c4 100644
--- a/app/models/observer/ticket/notification.rb
+++ b/app/models/observer/ticket/notification.rb
@@ -1,3 +1,5 @@
+require 'notification_factory'
+
 class Observer::Ticket::Notification < ActiveRecord::Observer
   observe :ticket, 'ticket::_article'