diff --git a/app/controllers/courses_controller.rb b/app/controllers/courses_controller.rb
index 106ba3dd4..aaf24eadb 100644
--- a/app/controllers/courses_controller.rb
+++ b/app/controllers/courses_controller.rb
@@ -1129,7 +1129,7 @@ class CoursesController < ApplicationController
 
   def validate_course_name
     tip_exception("课堂名称不能为空！") if params[:course][:name].blank?
-    if params[:subject_id].blank? || (@course && @course.subject.blank?)
+    if params[:subject_id].blank? && @course.blank? || (@course && @course.subject.blank?)
       tip_exception("课程名称不能为空！") if params[:course_list_name].blank?
       tip_exception("课堂名称应以课程名称开头命名") unless params[:course][:name].index(params[:course_list_name]) &&
         params[:course][:name].index(params[:course_list_name]) == 0
diff --git a/app/models/homework_common.rb b/app/models/homework_common.rb
index 112fc523b..f198a7143 100644
--- a/app/models/homework_common.rb
+++ b/app/models/homework_common.rb
@@ -36,7 +36,7 @@ class HomeworkCommon < ApplicationRecord
 
   validates :name, length: { maximum: 60 }
   validates :description, length: { maximum: 15000 }
-  validates :reference_answer, length: { maximum: 5000 }
+  validates :reference_answer, length: { maximum: 15000 }
 
   # after_update :update_activity
   before_destroy :update_homework_bank_quotes
diff --git a/app/views/attachment_histories/_attachment_history.json.jbuilder b/app/views/attachment_histories/_attachment_history.json.jbuilder
index afb359e08..285aced42 100644
--- a/app/views/attachment_histories/_attachment_history.json.jbuilder
+++ b/app/views/attachment_histories/_attachment_history.json.jbuilder
@@ -8,3 +8,4 @@ json.downloads_count attachment.downloads_count
 json.created_on attachment.created_on
 json.url attachment_path(attachment, type: 'history').gsub("/api","")
 json.is_pdf attachment.is_history_pdf?
+json.attachment_id attachment.attachment_id