diff --git a/src/puppet-web/injectio.js b/src/puppet-web/injectio.js
index ab0aba8d272c831fd43c095d2b9ec94a4f874267..1816b7954ec05509f1087ceababed67228eefc59 100644
--- a/src/puppet-web/injectio.js
+++ b/src/puppet-web/injectio.js
@@ -429,7 +429,7 @@ return (function(port) {
     // })
     window.addEventListener('unload', function(e) {
       // XXX only 1 event can be emitted here???
-      Wechaty.emit('unload', e)
+      Wechaty.emit('unload', String(e))
       // Wechaty.slog('emit unload')
       // Wechaty.emit('logout', e)
       // Wechaty.slog('emit logout')
diff --git a/test/puppet-web/browser.spec.js b/test/puppet-web/browser.spec.js
index 880c1190d21a04699e4564efa41337fe91d6b6ad..fb57823804eeeb08d2cf1e213feb0529692b57c8 100644
--- a/test/puppet-web/browser.spec.js
+++ b/test/puppet-web/browser.spec.js
@@ -144,9 +144,11 @@ test('Browser session save & load', function(t) {
       , head: HEAD
       , sessionFile: PROFILE
     })
+    t.pass('re-new Browser')
     yield b.init()
+    t.pass('re-init Browser')
     yield b.open()
-    t.pass('re-new/init/open Browser')
+    t.pass('re-open Browser')
 
     yield b.loadSession()
     t.pass('loadSession for new instance of Browser')