Ember.computed.equal returns false on identical strings

Is there something I don't understand or have I encountered a bug?

isCreator: Ember.computed.equal('session.user.id', 'model.user.id'), //false
isCreator2: Ember.computed('session.user.id','model.user.id', function(){  //true
                return this.get('session.user.id') === this.get('model.user.id');
        }),