diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 1a400312b..1df371b9b 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -4741,7 +4741,7 @@ end
 
 def get_hw_index(hw,is_teacher,type=0)
   homework_commons = hw.course.homework_commons
-  Rails.logger.info("----------------------------------------------"+hw.course)
+  Rails.logger.info("----------------------------------------------"+hw.course.to_s)
   if is_teacher
     if type != 0
       homeworks = homework_commons.where("homework_commons.homework_type = #{type}").order("created_at asc")