protected function _throwIfNotSupported()
    {
        $version = '2.0';
        $redisVersion = $this->_rediska->getOption('redisVersion');
        if (version_compare($version, $this->_rediska->getOption('redisVersion')) == 1) {
            throw new Rediska_Transaction_Exception("Transaction requires {$version}+ version of Redis server. Current version is {$redisVersion}. To change it specify 'redisVersion' option.");
        }
    }