diff --git a/system/libraries/Cache/drivers/Cache_redis.php b/system/libraries/Cache/drivers/Cache_redis.php
index 5236556..a35fbf6 100644
--- a/system/libraries/Cache/drivers/Cache_redis.php
+++ b/system/libraries/Cache/drivers/Cache_redis.php
@@ -111,7 +111,7 @@
 	{
 		if (is_array($data) OR is_object($data))
 		{
-			if ( ! $this->_redis->sAdd('_ci_redis_serialized', $id))
+			if ( ! $this->_redis->sIsMember('_ci_redis_serialized', $id) && ! $this->_redis->sAdd('_ci_redis_serialized', $id))
 			{
 				return FALSE;
 			}