diff --git a/src/ng/directive/input.js b/src/ng/directive/input.js
index 977be6c7bfa6..48e218f51e5b 100644
--- a/src/ng/directive/input.js
+++ b/src/ng/directive/input.js
@@ -1129,15 +1129,35 @@ function numberInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   });
 
   if (attr.min) {
+    var minVal;
     ctrl.$validators.min = function(value) {
-      return ctrl.$isEmpty(value) || isUndefined(attr.min) || value >= parseFloat(attr.min);
+      return ctrl.$isEmpty(value) || isUndefined(minVal) || value >= minVal;
     };
+
+    attr.$observe('min', function(val) {
+      if (isDefined(val) && !isNumber(val)) {
+        val = parseFloat(val, 10);
+      }
+      minVal = isNumber(val) && !isNaN(val) ? val : undefined;
+      // TODO(matsko): implement validateLater to reduce number of validations
+      ctrl.$validate();
+    });
   }
 
   if (attr.max) {
+    var maxVal;
     ctrl.$validators.max = function(value) {
-      return ctrl.$isEmpty(value) || isUndefined(attr.max) || value <= parseFloat(attr.max);
+      return ctrl.$isEmpty(value) || isUndefined(maxVal) || value <= maxVal;
     };
+
+    attr.$observe('max', function(val) {
+      if (isDefined(val) && !isNumber(val)) {
+        val = parseFloat(val, 10);
+      }
+      maxVal = isNumber(val) && !isNaN(val) ? val : undefined;
+      // TODO(matsko): implement validateLater to reduce number of validations
+      ctrl.$validate();
+    });
   }
 }
 
diff --git a/test/ng/directive/inputSpec.js b/test/ng/directive/inputSpec.js
index 3c5e6d437cb1..3bcf7a781edf 100644
--- a/test/ng/directive/inputSpec.js
+++ b/test/ng/directive/inputSpec.js
@@ -2894,18 +2894,28 @@ describe('input', function() {
         expect(scope.form.alias.$error.min).toBeFalsy();
       });
 
-      it('should validate even if min value changes on-the-fly', function(done) {
+      it('should validate even if min value changes on-the-fly', function() {
         scope.min = 10;
         compileInput('<input type="number" ng-model="value" name="alias" min="{{min}}" />');
 
-        changeInputValueTo('5');
+        changeInputValueTo('15');
+        expect(inputElm).toBeValid();
+
+        scope.min = 20;
+        scope.$digest();
         expect(inputElm).toBeInvalid();
 
-        scope.min = 0;
-        scope.$digest(function () {
-          expect(inputElm).toBeValid();
-          done();
-        });
+        scope.min = null;
+        scope.$digest();
+        expect(inputElm).toBeValid();
+
+        scope.min = '20';
+        scope.$digest();
+        expect(inputElm).toBeInvalid();
+
+        scope.min = 'abc';
+        scope.$digest();
+        expect(inputElm).toBeValid();
       });
     });
 
@@ -2926,7 +2936,7 @@ describe('input', function() {
         expect(scope.form.alias.$error.max).toBeFalsy();
       });
 
-      it('should validate even if max value changes on-the-fly', function(done) {
+      it('should validate even if max value changes on-the-fly', function() {
         scope.max = 10;
         compileInput('<input type="number" ng-model="value" name="alias" max="{{max}}" />');
 
@@ -2934,10 +2944,20 @@ describe('input', function() {
         expect(inputElm).toBeValid();
 
         scope.max = 0;
-        scope.$digest(function () {
-          expect(inputElm).toBeInvalid();
-          done();
-        });
+        scope.$digest();
+        expect(inputElm).toBeInvalid();
+
+        scope.max = null;
+        scope.$digest();
+        expect(inputElm).toBeValid();
+
+        scope.max = '4';
+        scope.$digest();
+        expect(inputElm).toBeInvalid();
+
+        scope.max = 'abc';
+        scope.$digest();
+        expect(inputElm).toBeValid();
       });
     });