diff --git a/src/ng/directive/input.js b/src/ng/directive/input.js
index 9ee879dc1890..acf5da543162 100644
--- a/src/ng/directive/input.js
+++ b/src/ng/directive/input.js
@@ -1770,13 +1770,24 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
    * Runs each of the registered validations set on the $validators object.
    */
   this.$validate = function() {
-    this.$$runValidators(ctrl.$modelValue, ctrl.$viewValue);
+    // ignore $validate before model initialized
+    if (ctrl.$modelValue !== ctrl.$modelValue) {
+      return;
+    }
+
+    var prev = ctrl.$modelValue;
+    ctrl.$$runValidators(ctrl.$$invalidModelValue || ctrl.$modelValue, ctrl.$viewValue);
+    if (prev !== ctrl.$modelValue) {
+      ctrl.$$writeModelToScope();
+    }
   };
 
   this.$$runValidators = function(modelValue, viewValue) {
     forEach(ctrl.$validators, function(fn, name) {
       ctrl.$setValidity(name, fn(modelValue, viewValue));
     });
+    ctrl.$modelValue         = ctrl.$valid ? modelValue : undefined;
+    ctrl.$$invalidModelValue = ctrl.$valid ? undefined : modelValue;
   };
 
   /**
@@ -1815,22 +1826,22 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
 
     if (ctrl.$modelValue !== modelValue &&
         (isUndefined(ctrl.$$invalidModelValue) || ctrl.$$invalidModelValue != modelValue)) {
-
       ctrl.$$runValidators(modelValue, viewValue);
-      ctrl.$modelValue         = ctrl.$valid ? modelValue : undefined;
-      ctrl.$$invalidModelValue = ctrl.$valid ? undefined : modelValue;
-
-      ngModelSet($scope, ctrl.$modelValue);
-      forEach(ctrl.$viewChangeListeners, function(listener) {
-        try {
-          listener();
-        } catch(e) {
-          $exceptionHandler(e);
-        }
-      });
+      ctrl.$$writeModelToScope();
     }
   };
 
+  this.$$writeModelToScope = function() {
+    ngModelSet($scope, ctrl.$modelValue);
+    forEach(ctrl.$viewChangeListeners, function(listener) {
+      try {
+        listener();
+      } catch(e) {
+        $exceptionHandler(e);
+      }
+    });
+  };
+
   /**
    * @ngdoc method
    * @name ngModel.NgModelController#$setViewValue
@@ -1909,8 +1920,6 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
       }
 
       ctrl.$$runValidators(modelValue, viewValue);
-      ctrl.$modelValue         = ctrl.$valid ? modelValue : undefined;
-      ctrl.$$invalidModelValue = ctrl.$valid ? undefined : modelValue;
 
       if (ctrl.$viewValue !== viewValue) {
         ctrl.$viewValue = ctrl.$$lastCommittedViewValue = viewValue;
diff --git a/test/ng/directive/inputSpec.js b/test/ng/directive/inputSpec.js
index c4acdc05a679..329079ffb622 100644
--- a/test/ng/directive/inputSpec.js
+++ b/test/ng/directive/inputSpec.js
@@ -294,27 +294,13 @@ describe('NgModelController', function() {
       };
 
       ctrl.$modelValue = 'test';
+      ctrl.$$invalidModelValue = undefined;
       ctrl.$validate();
 
       expect(ctrl.$valid).toBe(false);
 
       ctrl.$modelValue = 'TEST';
-      ctrl.$validate();
-
-      expect(ctrl.$valid).toBe(true);
-    });
-
-    it('should perform validations when $validate() is called', function() {
-      ctrl.$validators.uppercase = function(value) {
-        return (/^[A-Z]+$/).test(value);
-      };
-
-      ctrl.$modelValue = 'test';
-      ctrl.$validate();
-
-      expect(ctrl.$valid).toBe(false);
-
-      ctrl.$modelValue = 'TEST';
+      ctrl.$$invalidModelValue = undefined;
       ctrl.$validate();
 
       expect(ctrl.$valid).toBe(true);
@@ -403,6 +389,7 @@ describe('NgModelController', function() {
         };
       };
 
+      ctrl.$modelValue = undefined;
       ctrl.$validators.a = curry(true);
       ctrl.$validators.b = curry(true);
       ctrl.$validators.c = curry(false);
@@ -423,6 +410,7 @@ describe('NgModelController', function() {
         };
       };
 
+      ctrl.$modelValue = undefined;
       ctrl.$validators.unique = curry(false);
       ctrl.$validators.tooLong = curry(false);
       ctrl.$validators.notNumeric = curry(true);
@@ -1489,6 +1477,80 @@ describe('input', function() {
       expect(inputElm).toBeValid();
       expect(scope.form.input.$error.maxlength).not.toBe(true);
     });
+
+    it('should assign the correct model after an observed validator became valid', function() {
+      compileInput('<input type="text" name="input" ng-model="value" maxlength="{{ max }}" />');
+
+      scope.$apply(function() {
+        scope.max = 1;
+      });
+      changeInputValueTo('12345');
+      expect(scope.value).toBeUndefined();
+
+      scope.$apply(function() {
+        scope.max = 6;
+      });
+      expect(scope.value).toBe('12345');
+    });
+
+    it('should assign the correct model after an observed validator became invalid', function() {
+      compileInput('<input type="text" name="input" ng-model="value" maxlength="{{ max }}" />');
+
+      scope.$apply(function() {
+        scope.max = 6;
+      });
+      changeInputValueTo('12345');
+      expect(scope.value).toBe('12345');
+
+      scope.$apply(function() {
+        scope.max = 1;
+      });
+      expect(scope.value).toBeUndefined();
+    });
+
+    it('should leave the value as invalid if observed maxlength changed, but is still invalid', function() {
+      compileInput('<input type="text" name="input" ng-model="value" maxlength="{{ max }}" />');
+      scope.$apply(function() {
+        scope.max = 1;
+      });
+
+      changeInputValueTo('12345');
+      expect(inputElm).toBeInvalid();
+      expect(scope.form.input.$error.maxlength).toBe(true);
+      expect(scope.value).toBeUndefined();
+
+      scope.$apply(function() {
+        scope.max = 3;
+      });
+
+      expect(inputElm).toBeInvalid();
+      expect(scope.form.input.$error.maxlength).toBe(true);
+      expect(scope.value).toBeUndefined();
+    });
+
+    it('should not notify if observed maxlength changed, but is still invalid', function() {
+      compileInput('<input type="text" name="input" ng-model="value" ng-change="ngChangeSpy()" ' +
+                   'maxlength="{{ max }}" />');
+
+      scope.$apply(function() {
+        scope.max = 1;
+      });
+      changeInputValueTo('12345');
+
+      scope.ngChangeSpy = jasmine.createSpy();
+      scope.$apply(function() {
+        scope.max = 3;
+      });
+
+      expect(scope.ngChangeSpy).not.toHaveBeenCalled();
+    });
+
+    it('should leave the model untouched when validating before model initialization', function() {
+      scope.value = '12345';
+      compileInput('<input type="text" name="input" ng-model="value" minlength="3" />');
+      expect(scope.value).toBe('12345');
+    });
+
   });