diff --git a/lib/directive/ng_model.dart b/lib/directive/ng_model.dart
index 1b6797ab6..239b2e68b 100644
--- a/lib/directive/ng_model.dart
+++ b/lib/directive/ng_model.dart
@@ -28,6 +28,10 @@ class NgModel extends NgControl implements NgAttachAware {
     _exp = 'ng-model=${attrs["ng-model"]}';
   }
 
+  process(value) {
+    render(value);
+    validate();
+  }
 
   attach() {
     watchCollection = false;
@@ -51,9 +55,9 @@ class NgModel extends NgControl implements NgAttachAware {
     _watchCollection = value;
     _removeWatch();
     if (_watchCollection) {
-      _removeWatch = _scope.$watchCollection((s) => getter(), (value) => render(value), _exp);
+      _removeWatch = _scope.$watchCollection((s) => getter(), (value) => process(value), _exp);
     } else {
-      _removeWatch = _scope.$watch((s) => getter(), (value) => render(value), _exp);
+      _removeWatch = _scope.$watch((s) => getter(), (value) => process(value), _exp);
     }
   }
 
diff --git a/test/directive/ng_model_spec.dart b/test/directive/ng_model_spec.dart
index 41373c351..9240ad1c1 100644
--- a/test/directive/ng_model_spec.dart
+++ b/test/directive/ng_model_spec.dart
@@ -758,6 +758,41 @@ describe('ng-model', () {
     }));
   });
 
+  describe('validation', () {
+    it('should happen automatically when the scope changes', inject((Scope scope) {
+      _.compile('<input type="text" ng-model="model" probe="i" required>');
+      _.rootScope.$digest();
+
+      Probe probe = _.rootScope.i;
+      var model = probe.directive(NgModel);
+
+      expect(model.invalid).toBe(true);
+      expect(model.valid).toBe(false);
+
+      _.rootScope.$apply('model = "viljami"');
+
+      expect(model.invalid).toBe(false);
+      expect(model.valid).toBe(true);
+    }));
+
+    it('should happen automatically upon user input via the onInput event', inject(() {
+      _.compile('<input type="text" ng-model="model" probe="i" required>');
+
+      Probe probe = _.rootScope.i;
+      var model = probe.directive(NgModel);
+      InputElement inputElement = model.element;
+
+      expect(model.invalid).toBe(true);
+      expect(model.valid).toBe(false);
+
+      inputElement.value = 'some value';
+      _.triggerEvent(inputElement, 'input');
+
+      expect(model.invalid).toBe(false);
+      expect(model.valid).toBe(true);
+    }));
+  });
+
   describe('valid / invalid', () {
     it('should add and remove the correct flags when set to valid and to invalid', inject((Scope scope) {
       _.compile('<input type="text" ng-model="my_model" probe="i" />');