protected function _throwIfNotSupported()
    {
        $version = '1.3.8';
        $redisVersion = $this->getRediska()->getOption('redisVersion');
        if (version_compare($version, $this->getRediska()->getOption('redisVersion')) == 1) {
            throw new Rediska_PubSub_Exception("Publish/Subscribe requires {$version}+ version of Redis server. Current version is {$redisVersion}. To change it specify 'redisVersion' option.");
        }
    }