Ember "No model was found for `user-role?`"

I added a new model in Ember called user-role. It's no different to any of the other 30+ models the app has. But out of the blue I get this error in the console:

No model was found for 'user-role'

I get this error when I'm requesting the user model from the API. user model has a hasMany relationship to user-role models.

Our user model already has at least three hasMany relationships to other similar models and they work just fine. I'm completely lost why this is happening.

UPDATE almost two hours later I renamed the user-role model to userrole and everything works as expected. I've been using Ember for over two years almost on a daily basis and I'm still lost with their naming conventions. user model also has a hasMany relationship to user-relationship model and it works just fine. There must be some difference how the data is loaded from the API.