diff --git a/samples/oauth2/appengine/main.py b/samples/oauth2/appengine/main.py
index 78634e7..f037bb8 100644
--- a/samples/oauth2/appengine/main.py
+++ b/samples/oauth2/appengine/main.py
@@ -48,21 +48,7 @@
     credentials = StorageByKeyName(
         Credentials, user.user_id(), 'credentials').get()
 
-    if credentials:
-      http = httplib2.Http()
-      http = credentials.authorize(http)
-      p = build("buzz", "v1", http=http)
-      activities = p.activities()
-      activitylist = activities.list(scope='@consumption',
-                                     userId='@me').execute()
-      path = os.path.join(os.path.dirname(__file__), 'welcome.html')
-      logout = users.create_logout_url('/')
-      self.response.out.write(
-          template.render(
-              path, {'activitylist': activitylist,
-                     'logout': logout
-                     }))
-    else:
+    if credentials is None or credentials.invalid == True:
       flow = OAuth2WebServerFlow(
           # Visit https://code.google.com/apis/console to
           # generate your client_id, client_secret and to
@@ -78,6 +64,20 @@
       authorize_url = flow.step1_get_authorize_url(callback)
       memcache.set(user.user_id(), pickle.dumps(flow))
       self.redirect(authorize_url)
+    else:
+      http = httplib2.Http()
+      http = credentials.authorize(http)
+      p = build("buzz", "v1", http=http)
+      activities = p.activities()
+      activitylist = activities.list(scope='@consumption',
+                                     userId='@me').execute()
+      path = os.path.join(os.path.dirname(__file__), 'welcome.html')
+      logout = users.create_logout_url('/')
+      self.response.out.write(
+          template.render(
+              path, {'activitylist': activitylist,
+                     'logout': logout
+                     }))
 
 
 class OAuthHandler(webapp.RequestHandler):
diff --git a/samples/oauth2/buzz/buzz.py b/samples/oauth2/buzz/buzz.py
index fe30a32..a009517 100644
--- a/samples/oauth2/buzz/buzz.py
+++ b/samples/oauth2/buzz/buzz.py
@@ -27,7 +27,7 @@
 def main():
   storage = Storage('buzz.dat')
   credentials = storage.get()
-  if not credentials:
+  if credentials is None or credentials.invalid == True:
     flow = OAuth2WebServerFlow(
         client_id='433807057907.apps.googleusercontent.com',
         client_secret='jigtZpMApkRxncxikFpR+SFg',
diff --git a/samples/oauth2/django_sample/buzz/views.py b/samples/oauth2/django_sample/buzz/views.py
index b59a334..f6903b7 100644
--- a/samples/oauth2/django_sample/buzz/views.py
+++ b/samples/oauth2/django_sample/buzz/views.py
@@ -22,7 +22,7 @@
 def index(request):
   storage = Storage(CredentialsModel, 'id', request.user, 'credential')
   credential = storage.get()
-  if credential is None:
+  if credential is None or credential.invalid == True:
     flow = OAuth2WebServerFlow(
         client_id='837647042410.apps.googleusercontent.com',
         client_secret='+SWwMCL9d8gWtzPRa1lXw5R8',
@@ -47,6 +47,7 @@
                 'activitylist': activitylist,
                 })
 
+
 @login_required
 def auth_return(request):
     try:
diff --git a/samples/oauth2/latitude/latitude.py b/samples/oauth2/latitude/latitude.py
index fc312dd..e0458f4 100644
--- a/samples/oauth2/latitude/latitude.py
+++ b/samples/oauth2/latitude/latitude.py
@@ -26,7 +26,7 @@
   storage = Storage('latitude.dat')
   credentials = storage.get()
 
-  if not credentials:
+  if credentials is None or credentials.invalid:
     flow = OAuth2WebServerFlow(
         client_id='433807057907.apps.googleusercontent.com',
         client_secret='jigtZpMApkRxncxikFpR+SFg',
diff --git a/samples/oauth2/moderator/moderator.py b/samples/oauth2/moderator/moderator.py
index 5a6e2b8..ae6c6d3 100644
--- a/samples/oauth2/moderator/moderator.py
+++ b/samples/oauth2/moderator/moderator.py
@@ -26,7 +26,7 @@
   storage = Storage('moderator.dat')
   credentials = storage.get()
 
-  if not credentials:
+  if credentials is None or credentials.invalid == True:
     flow = OAuth2WebServerFlow(
         client_id='433807057907.apps.googleusercontent.com',
         client_secret='jigtZpMApkRxncxikFpR+SFg',
diff --git a/samples/oauth2/urlshortener/main.py b/samples/oauth2/urlshortener/main.py
index 41677fb..e129069 100644
--- a/samples/oauth2/urlshortener/main.py
+++ b/samples/oauth2/urlshortener/main.py
@@ -37,26 +37,6 @@
 
     credentials = run(flow, storage)
 
-
-#  # Test AccessTokenCredentials
-#  at_credentials = AccessTokenCredentials(
-#      credentials.access_token, 'urlshortener-cmdline-sample/1.0')
-#  http = httplib2.Http()
-#  http = at_credentials.authorize(http)
-#
-#  # Build the url shortener service
-#  service = build("urlshortener", "v1", http=http,
-#            developerKey="AIzaSyDRRpR3GS1F1_jKNNM9HCNd2wJQyPG3oN0")
-#  url = service.url()
-#
-#  # Create a shortened URL by inserting the URL into the url collection.
-#  body = {"longUrl": "http://code.google.com/apis/urlshortener/" }
-#  resp = url.insert(body=body).execute()
-#  pprint.pprint(resp)
-#  http = httplib2.Http()
-#  http = credentials.authorize(http)
-#
-
   http = httplib2.Http()
   http = credentials.authorize(http)
 
@@ -77,7 +57,5 @@
   pprint.pprint(resp)
 
 
-
-
 if __name__ == '__main__':
   main()