Rails- Migrating from AuthLogic to Devise

As the title suggests, I'm attempting to migrate a Rails application from AuthLogic to Devise. I've followed along as outlined in http://ift.tt/1J1HJd9, but I am having difficulty when trying to use my existing user_sessions controller. I have removed the new, create and destroy methods as suggested, and I have updated the new.html.erb to user @user instead of @user_session. However, when I enter the credentials into the form and hit login, I get:

Could not find devise mapping for path "/user_session".

Is there something else I have to update to get this working?