AngularJS Form Validation

I have a angular directive to compare password with confirm password field. That directive works fine but I am unable to hide "Password does not match" error message.The error message goes away once I type the email text field which is a required field and comes after repeat password input. So it seems $invalid is related to form but not to the individual field. How can I relate the error specific to the two textboxes?

<div ng-show="!Enabled" class="form-group">
   <label class="col-md-3 control-label"><strong>Password</strong></label>
   <div class="col-md-6">
      <input type="password" id="updatedata.password" name="updatedata.password" class="form-control input-sm requiredpop" ng-model="updatedata.password" placeholder="Password" required>
   </div>
</div>
<div ng-show="!Enabled" class="form-group">
   <label class="col-md-3 control-label"><strong>Repeat Password</strong></label>
   <div class="col-md-6">
      <input type="password" id="updatedata.newpassword" name="updatedata.newpassword" class="form-control passpop input-sm" ng-model="updatedata.newpassword" password-match="updatedata.password" placeholder="Password" required>
      <p style="color:red" ng-show="!updateForm.updatedata.newpassword.$invalid">Password Does not match</p>
   </div>
</div>
<div class="form-group">
   <label class="col-md-3 control-label"><strong>Email</strong></label>
   <div class="col-md-9">
      <input type="email" ng-model="updatedata.Email" class="control-label requiredpop" placeholder="enter valid email address" required>
   </div>
</div>
appDirectives.directive('passwordMatch', [function () {
    return {
        restrict: 'A',
        scope: true,
        require: 'ngModel',
        link: function (scope, elem, attrs, control) {
            var checker = function () {

                //get the value of the first password
                var e1 = scope.$eval(attrs.ngModel);

                //get the value of the other password  
                var e2 = scope.$eval(attrs.passwordMatch);
                return e1 == e2;
            };
            scope.$watch(checker, function (n) {

                //set the form control to valid if both 
                //passwords are the same, else invalid
                control.$setValidity("unique", n);
            });
        }
    };
}]);

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