Password Confirmation AngularJS directive

passwordConfirmation.js

/*
How to use:
    on inputs:
        <input type="password" id="pw2" name="pw2"
            ng-model="pw2" ng-required="" password-confirm="pw1" />
    get errors with:
        "myForm.pw2.$error.passwordmatch"
*/
angular.module('myApp')
    .directive('passwordConfirm', [function () {
        return {
            require: 'ngModel',
            link: function (scope, elem, attrs, ctrl) {
                var me = attrs.ngModel;
                var matchTo = attrs.passwordConfirm;

                scope.$watch('[me, matchTo]', function(value){
                    ctrl.$setValidity('passwordmatch', scope.$eval(me) === scope.$eval(matchTo) );

                });
            }
        };
    }]);