diff --git a/app/controllers/files_controller.rb b/app/controllers/files_controller.rb
index 77ed9567d..117475894 100644
--- a/app/controllers/files_controller.rb
+++ b/app/controllers/files_controller.rb
@@ -18,7 +18,7 @@ class FilesController < ApplicationController
     sort_type = params[:sort_type] || 'created_on' # created_on：时间排序， downloads：下载次数排序; quotes: 引用次数排序
     @course_second_category_id = params[:course_second_category_id] || 0 # 0: 为主目录， 其他为次目录id
     @user = current_user
-    @attachments = @course_second_category_id.to_i == 0 ? @course.attachments.includes(:course_second_category) : @course.attachments.by_course_second_category_id(course_second_category_id)
+    @attachments = @course_second_category_id.to_i == 0 ? @course.attachments.includes(:course_second_category) : @course.attachments.by_course_second_category_id(@course_second_category_id)
     @attachments = @attachments.includes(author: [:user_extension, :course_members])
                        .ordered(sort: sort.to_i, sort_type: sort_type.strip)