deployer: Deploy fails with multiplexing enabled

• Deployer version: 6.8.0
• Deployment OS: Debian 9.13

export APP_ENV='stage' APP_DEBUG='0'; if [ -f /var/www/*************/.dep/deploy.lock ]; then echo 'true'; fi
< ssh multiplexing initialization
< Warning: Permanently added '**************,***.***.***.**' (ECDSA) to the list of known hosts.
< unix_listener: cannot bind to path /root/.ssh/deployer_deployer@**************.LiZt386qtCUqfmHr: No such file or directory

deploy example:

host('**************')
    ->stage('stage')
    ->set('deploy_path', '/var/www/stage-{{application}}')
    ->multiplexing(true)
    ->addSshOption('UserKnownHostsFile', '/dev/null')
    ->addSshOption('StrictHostKeyChecking', 'no')
    ->user('deployer');

when i disable multiplexing it works again