Service does not keep running after being started, while node process does

[amberv0]

The problem is following. I install the service:

sudo forever-service install appname --script app.js --scriptOptions " --prod --port 1338" --foreverOptions " -w" --start

This gives no error. But then when I check the status with
sudo service appname status
I get appname is not running. But the started app actually IS running, and so everything works as should. But if I try to start the service (since I do want watching on file changes and so on), I'll get the error because the port is already in use.
I don't know by what this is caused, but it looks like the service somehow starts the node script and then disconnects from it.
I'm using CentOS 6.8
forever-service version 0.5.8