Can't import styles from add-on after migrating to module unification structure in an ember app

I used the ember-module-migrator to migrate an Ember app to the new file structure and followed the instructions here: https://github.com/emberjs/ember.js/issues/16373.. Now when running the tests or the app i get a lot of errors of course :P but the following error is making me crazier than normal:

Error: Can't find stylesheet to import.
@import 'kci-style/addon';

but the addon is present in the node_modules folder.
I suspect that this might be related to that the addon is still using the old file structure...
I made sure that I have setup the fallback resolver correctly (as mentioned here: https://github.com/rwjblue/ember-module-migrator) but it still won't import the styles from the addon...

I even tried migrating the addon in the node_modules to the module unification structure but that also didn't help... any suggestions would be appreciated.

Thanks in advance...