Services.traefik.ports.0 must be a string or number - docker-app.yml

So been reading up on the Penguins work, great stuff!
But when I get to the part where you’re supposed to setup traefik-app.yml, I get the error above.

$ docker stack deploy traefik-app -c traefik-app.yml
services.traefik.ports.0 must be a string or number

What can I do about this? It seems to be something about the ports section and well I am lost. :slight_smile: