diff --git a/src/message-media.js b/src/message-media.js
index 22a4def59a1e53ccc7a691574e9edc511ae3a240..903087301ef8b6d0b1b0da8319a06af6a3af7153 100644
--- a/src/message-media.js
+++ b/src/message-media.js
@@ -1,59 +1,59 @@
-/**
- *
- * wechaty: Wechat for Bot. and for human who talk to bot/robot
- *
- * Licenst: ISC
- * https://github.com/zixia/wechaty
- *
- */
-const co = require('co')
-
-const log = require('./brolog-env')
-const UtilLib = require('./util-lib')
-const Message = require('./message')
-
-class MediaMessage extends Message {
-  constructor(rawObj) {
-    super(rawObj)
-    this.bridge = Message.puppet.bridge
-  }
-  ready() {
-    log.silly('MediaMessage', 'ready()')
-
-    const parentReady = super.ready.bind(this)
-    return co.call(this, function* () {
-      yield parentReady()
-      const url = yield this.getMsgImg(this.id)
-      this.obj.url = url
-
-      return this // IMPORTANT!
-    })
-    .catch(e => {
-      log.warn('MediaMessage', 'ready() exception: %s', e.message)
-      throw e
-    })
-  }
-  getMsgImg(id) {
-    return this.bridge.getMsgImg(id)
-    .catch(e => {
-      log.warn('MediaMessage', 'getMsgImg(%d) exception: %s', id, e.message)
-      throw e
-    })
-  }
-
-  readyStream() {
-    return this.ready()
-    .then(() => {
-      return Message.puppet.browser.checkSession()
-    })
-    .then(cookies => {
-      return UtilLib.downloadStream(this.obj.url, cookies)
-    })
-    .catch(e => {
-      log.warn('MediaMessage', 'stream() exception: %s', e.message)
-      throw e
-    })
-  }
-}
-
-module.exports = MediaMessage
+/**
+ *
+ * wechaty: Wechat for Bot. and for human who talk to bot/robot
+ *
+ * Licenst: ISC
+ * https://github.com/zixia/wechaty
+ *
+ */
+const co = require('co')
+
+const log = require('./brolog-env')
+const UtilLib = require('./util-lib')
+const Message = require('./message')
+
+class MediaMessage extends Message {
+  constructor(rawObj) {
+    super(rawObj)
+    this.bridge = Message.puppet.bridge
+  }
+  ready() {
+    log.silly('MediaMessage', 'ready()')
+
+    const parentReady = super.ready.bind(this)
+    return co.call(this, function* () {
+      yield parentReady()
+      const url = yield this.getMsgImg(this.id)
+      this.obj.url = url
+
+      return this // IMPORTANT!
+    })
+    .catch(e => {
+      log.warn('MediaMessage', 'ready() exception: %s', e.message)
+      throw e
+    })
+  }
+  getMsgImg(id) {
+    return this.bridge.getMsgImg(id)
+    .catch(e => {
+      log.warn('MediaMessage', 'getMsgImg(%d) exception: %s', id, e.message)
+      throw e
+    })
+  }
+
+  readyStream() {
+    return this.ready()
+    .then(() => {
+      return Message.puppet.browser.checkSession()
+    })
+    .then(cookies => {
+      return UtilLib.downloadStream(this.obj.url, cookies)
+    })
+    .catch(e => {
+      log.warn('MediaMessage', 'stream() exception: %s', e.message)
+      throw e
+    })
+  }
+}
+
+module.exports = MediaMessage.default = MediaMessage.MediaMessage = MediaMessage