diff --git a/src/puppet-web/browser-driver.ts b/src/puppet-web/browser-driver.ts
index 6921c0fc53db00f6c1c863562817db85b54faac9..313940bd7c23416066279acb372bc65b56f7ed34 100644
--- a/src/puppet-web/browser-driver.ts
+++ b/src/puppet-web/browser-driver.ts
@@ -251,41 +251,52 @@ export class BrowserDriver {
          */
         const TIMEOUT = 7 * 1000
 
-        let timer: NodeJS.Timer | null
+        let watchdogTimer: NodeJS.Timer | null
 
-        timer = setTimeout(() => {
+        watchdogTimer = setTimeout(() => {
           const e = new Error('valid() driver.getSession() timeout(halt?)')
           log.warn('PuppetWebBrowserDriver'   , e.message)
 
           // record timeout by set timer to null
-          timer = null
+          watchdogTimer = null
 
           // 1. Promise rejected
-          return reject(e)
+          reject(e)
+          return
 
         }, TIMEOUT)
 
         log.verbose('PuppetWebBrowserDriver', 'valid() getSession()')
         driver.getSession()
               .then(session => {
-                log.verbose('PuppetWebBrowserDriver', 'valid() getSession() done')
-                if (timer) {
-                  clearTimeout(timer)
-                  timer = null
+                log.verbose('PuppetWebBrowserDriver', 'valid() getSession() then() done')
+                if (watchdogTimer) {
+                  log.verbose('PuppetWebBrowserDriver', 'valid() getSession() then() watchdog timer exist, will be cleared')
+                  clearTimeout(watchdogTimer)
+                  watchdogTimer = null
+                } else {
+                  log.verbose('PuppetWebBrowserDriver', 'valid() getSession() then() watchdog timer not exist?')
                 }
 
                 // 2. Promise resolved
-                return resolve(session)
+                resolve(session)
+                return
 
               })
               .catch(e => {
-                log.warn('PuppetWebBrowserDriver', 'valid() getSession() rejected: %s', e && e.message || e)
+                log.warn('PuppetWebBrowserDriver', 'valid() getSession() catch() rejected: %s', e && e.message || e)
 
-                // 3. Promise rejected
-                if (timer) {
-                  // do not call reject again if there's already a timeout
-                  timer = null
-                  return reject(e)
+                // do not call reject again if there's already a timeout
+                if (watchdogTimer) {
+                  log.verbose('PuppetWebBrowserDriver', 'valid() getSession() catch() watchdog timer exist, will set it to null and call reject()')
+
+                  // 3. Promise rejected
+                  watchdogTimer = null
+                  reject(e)
+                  return
+
+                } else {
+                  log.verbose('PuppetWebBrowserDriver', 'valid() getSession() catch() watchdog timer not exist, will not call reject() again')
                 }
 
               })
diff --git a/test/webdriver.spec.ts b/test/webdriver.spec.ts
index 7c811241c89a6f11840333f3ee9a3b85e6569d6c..05ae5034e6a74ed346e247817d4b5c02b20e725c 100644
--- a/test/webdriver.spec.ts
+++ b/test/webdriver.spec.ts
@@ -13,9 +13,9 @@ import { test }   from 'ava'
 // }                 from 'selenium-webdriver'
 
 import {
-    Bridge
-  , Browser
-  , PuppetWeb
+  Bridge,
+  Browser,
+  PuppetWeb,
 } from '../src/puppet-web/'
 
 /**