diff --git a/app/controllers/shixuns_controller.rb b/app/controllers/shixuns_controller.rb
index 8359b14f9..a809e8d2b 100644
--- a/app/controllers/shixuns_controller.rb
+++ b/app/controllers/shixuns_controller.rb
@@ -409,7 +409,7 @@ class ShixunsController < ApplicationController
 	end
 
 	def propaedeutics
-		@content = Shixun.where(identifier: params[:identifier]).pluck(:propaedeutics)
+		@content = Shixun.find_by_identifier!(params[:identifier]).propaedeutics
 	end
 
 	# 更新背景知识