diff --git a/app/decorators/tiding_decorator.rb b/app/decorators/tiding_decorator.rb
index 81093dc12..d43aa5e2d 100644
--- a/app/decorators/tiding_decorator.rb
+++ b/app/decorators/tiding_decorator.rb
@@ -86,7 +86,7 @@ module TidingDecorator
 
   def teacher_join_course_content
     name = Course.find_by(id: container_id)&.name
-    I18n.t(locale_format extra) % [user.show_real_name, name]
+    I18n.t(locale_format extra) % [trigger_user&.show_real_name, name]
   end
 
   def apply_add_department_content