diff --git a/examples/ding-dong-bot.ts b/examples/ding-dong-bot.ts
index d6dda96ac00b78faceeabd8f504cdc80aeca304c..4efba04b0a7c51520740eec7ab9d6fb2d581e269 100644
--- a/examples/ding-dong-bot.ts
+++ b/examples/ding-dong-bot.ts
@@ -72,16 +72,20 @@ bot.start()
  *
  */
 function onScan (qrcode: string, status: ScanStatus) {
-  generate(qrcode)
-
-  // Generate a QR Code online via
-  // http://goqr.me/api/doc/create-qr-code/
-  const qrcodeImageUrl = [
-    'https://api.qrserver.com/v1/create-qr-code/?data=',
-    encodeURIComponent(qrcode),
-  ].join('')
-
-  console.info('%s(%s) - %s', ScanStatus[status], status, qrcodeImageUrl)
+  if (status === ScanStatus.Waiting || status === ScanStatus.Timeout) {
+    generate(qrcode)
+
+    // Generate a QR Code online via
+    // http://goqr.me/api/doc/create-qr-code/
+    const qrcodeImageUrl = [
+      'https://api.qrserver.com/v1/create-qr-code/?data=',
+      encodeURIComponent(qrcode),
+    ].join('')
+
+    console.info('onScan: %s(%s) - %s', ScanStatus[status], status, qrcodeImageUrl)
+  } else {
+    console.info('onScan: %s(%s)', ScanStatus[status], status)
+  }
 
   // console.info(`[${ScanStatus[status]}(${status})] ${qrcodeImageUrl}\nScan QR Code above to log in: `)
 }
diff --git a/package.json b/package.json
index c6921c24321bf6cff97e8a570e2b59e7439b9605..5e6e97263bdc89143efc67223a407e0c98353692 100644
--- a/package.json
+++ b/package.json
@@ -80,7 +80,7 @@
   },
   "dependencies": {
     "brolog": "^1.8.1",
-    "clone-class": "^0.6.11",
+    "clone-class": "^0.7.3",
     "cuid": "^2.1.1",
     "hot-import": "^0.2.1",
     "in-gfw": "^1.2.0",
diff --git a/src/accessory.ts b/src/accessory.ts
index 839529866d880f6ae1b9a6fae7844617a55a9f18..dde5a94169bd39ed5999aabda6793b3ae55a4ee8 100644
--- a/src/accessory.ts
+++ b/src/accessory.ts
@@ -9,8 +9,8 @@ import { Wechaty }  from './wechaty'
 // use Symbol to prevent conflicting with the child class properties
 // This symbol must be exported (for now).
 // See: https://github.com/Microsoft/TypeScript/issues/20080
-export const SYMBOL_NAME    = Symbol('name')
-export const SYMBOL_COUNTER = Symbol('counter')
+const SYMBOL_NAME    = Symbol('name')
+const SYMBOL_COUNTER = Symbol('counter')
 
 let COUNTER = 0
 
@@ -155,6 +155,7 @@ export abstract class Accessory extends EventEmitter {
    *  FriendRequest.wechaty
    *  Message.wechaty
    *  Room.wechaty
+   *  ... etc
    *
    * So it only need one `wechaty` for all the instances
    */