diff --git a/app/controllers/wechats_controller.rb b/app/controllers/wechats_controller.rb
index 2cb114a56..7e87d353c 100644
--- a/app/controllers/wechats_controller.rb
+++ b/app/controllers/wechats_controller.rb
@@ -8,6 +8,7 @@ class WechatsController < ActionController::Base
   # default text responder when no other match
   on :text do |request, content|
       #邀请码
+    begin
       uw = user_binded?(request[:FromUserName])
       if !uw
         sendBind()
@@ -25,6 +26,9 @@ class WechatsController < ActionController::Base
       else
         request.reply.text "您的意见已收到，感谢您的反馈！" # Just echo
       end
+    rescue => e
+      request.reply.text e
+    end
   end
 
   # When receive 'help', will trigger this responder
@@ -183,9 +187,12 @@ class WechatsController < ActionController::Base
 
   def join_class(content, user)
     cs = CoursesService.new
-    status = cs.join_course({invite_code: content.strip}, current_user)
+    status = cs.join_course({invite_code: content.upcase.strip}, current_user)
     logger.info status
-    status[:state] == 0 ? status[:course] : nil
+    if status[:state] != 0
+      raise CoursesService::JoinCourseError.message(status[:state])
+    end
+    status[:course]
   end
 
   ###  controller method