elm-reactor gives 404

[lazywithclass]

I am learning elm and so I've started with the first example.

I am using elm-reactor (v 0.16.0) so I can try to change something and see the result. I am starting elm-reactor from elm-architecture-tutorial/examples/1 but each time I am getting

{
  "statusCode": 404,
  "error": "Not Found"
}

I am not really sure what I am doing wrong; if I run elm-make I correctly get index.html though.

Do you have any suggestions / hints?

[lazywithclass]

For some reason I had a few of those running on 8000, once killed everything started working.