diff --git a/app/models/homework_common.rb b/app/models/homework_common.rb
index b56406f19..925ebb106 100644
--- a/app/models/homework_common.rb
+++ b/app/models/homework_common.rb
@@ -3,6 +3,7 @@
 class HomeworkCommon < ActiveRecord::Base
   # attr_accessible :name, :user_id, :description, :publish_time, :end_time, :homework_type, :late_penalty, :course_id
   include Redmine::SafeAttributes
+  include ApplicationHelper
 
   belongs_to :course
   belongs_to :user