diff --git a/appengine/memcache/guestbook/main.py b/appengine/memcache/guestbook/main.py
index 958c5e7230fc..e9c289020bf2 100644
--- a/appengine/memcache/guestbook/main.py
+++ b/appengine/memcache/guestbook/main.py
@@ -127,6 +127,7 @@ def post(self):
 
         greeting.content = self.request.get('content')
         greeting.put()
+        memcache.delete('{}:greetings'.format(guestbook_name))
         self.redirect('/?' +
                       urllib.urlencode({'guestbook_name': guestbook_name}))