diff --git a/src/Stash/Driver/Sub/Memcached.php b/src/Stash/Driver/Sub/Memcached.php
index 51b8beda..d8066cac 100644
--- a/src/Stash/Driver/Sub/Memcached.php
+++ b/src/Stash/Driver/Sub/Memcached.php
@@ -186,7 +186,7 @@ public function get($key)
      */
     public function cas($key, $value)
     {
-        $token = null;
+        $token = 0;
         if (($rValue = $this->memcached->get($key, null, $token)) !== false) {
             return $rValue;
         }