@Rakinare Jup, I needed to add a field to the Profile. This broke the saves. Should have really told you before. I will make a mental note to do so in the future . If stopping the server and deleting the profiles.yml doesn't solve the error, please post the full stacktrace. EDIT: Have you tried what I suggested? "the error should only occur if your profiles.yml is outdated. It works for me if I stop the server and delete the profiles.yml. If it doesn't work, reply to this please."