diff --git a/app/controllers/messages_controller.rb b/app/controllers/messages_controller.rb
index 4cd546b3b..5481f582e 100644
--- a/app/controllers/messages_controller.rb
+++ b/app/controllers/messages_controller.rb
@@ -103,7 +103,7 @@ class MessagesController < ApplicationController
     return normal_status(403, "您没有权限进行该操作") if current_user != @message.author && !current_user.teacher_of_course?(@message.board.course)
 
     begin
-      board_id = @course.boards.find_by(id: params[:select_board_id])
+      board_id = @message.board&.course&.boards.find_by(id: params[:select_board_id])
 
       email_notify = @message.email_notify ? 1 : @message.board&.course.email_notify && params[:email_notify]
       send_email = !@message.email_notify && email_notify