protected function getBucket()
    {
        if (empty($this->sS3Bucket)) {
            $this->sS3Bucket = $this->getRegionAndBucket()->bucket;
            if (empty($this->sS3Bucket)) {
                throw new DriverException('S3 Bucket has not been defined.');
            }
        }

        return $this->sS3Bucket;
    }