diff --git a/shared/db/Maintenance.ts b/shared/db/Maintenance.ts
index 389e2b156..99a8393f9 100644
--- a/shared/db/Maintenance.ts
+++ b/shared/db/Maintenance.ts
@@ -25,13 +25,13 @@ export default class Maintenance extends BaseModel {
     @prop({ required: true })
     startTime: Date;       // 维护开始时间
 
-    @prop({ ref: 'Marquee', type: mongoose.Schema.Types.ObjectId })
+    @prop({ ref: () => Marquee, type: mongoose.Schema.Types.ObjectId })
     marquee: Ref<Marquee>;      // 跑马灯，连接到marquee表
 
-    @prop({ ref: 'Notice', type: mongoose.Schema.Types.ObjectId })
+    @prop({ ref: () => Notice, type: mongoose.Schema.Types.ObjectId })
     notice: Ref<Notice>;        // 维护公告
 
-    @prop({ ref: 'GMMail', type: mongoose.Schema.Types.ObjectId })
+    @prop({ ref: () => GMMail, type: mongoose.Schema.Types.ObjectId })
     mail: Ref<GMMail>;          // 维护结束邮件