diff --git a/modules/angular2/src/core/forms/directives/abstract_control_directive.ts b/modules/angular2/src/core/forms/directives/abstract_control_directive.ts
index 235816ebac..05fe23bc0b 100644
--- a/modules/angular2/src/core/forms/directives/abstract_control_directive.ts
+++ b/modules/angular2/src/core/forms/directives/abstract_control_directive.ts
@@ -1,8 +1,9 @@
 import {AbstractControl} from '../model';
 import {isPresent} from 'angular2/src/core/facade/lang';
+import {unimplemented} from 'angular2/src/core/facade/exceptions';
 
-export class AbstractControlDirective {
-  get control(): AbstractControl { return null; }
+export abstract class AbstractControlDirective {
+  get control(): AbstractControl { return unimplemented(); }
 
   get value(): any { return isPresent(this.control) ? this.control.value : null; }
 
diff --git a/modules/angular2/src/core/forms/directives/ng_control.ts b/modules/angular2/src/core/forms/directives/ng_control.ts
index a2574aabca..cc175b7bd8 100644
--- a/modules/angular2/src/core/forms/directives/ng_control.ts
+++ b/modules/angular2/src/core/forms/directives/ng_control.ts
@@ -10,11 +10,11 @@ import {unimplemented} from 'angular2/src/core/facade/exceptions';
 // an abstract method in the public API, and we cannot reflect
 // on that in Dart due to https://github.com/dart-lang/sdk/issues/18721
 // Also we don't have abstract setters, see https://github.com/Microsoft/TypeScript/issues/4669
-export class NgControl extends AbstractControlDirective {
+export abstract class NgControl extends AbstractControlDirective {
   name: string = null;
   valueAccessor: ControlValueAccessor = null;
 
   get validator(): Function { return unimplemented(); }
 
-  viewToModelUpdate(newValue: any): void { return unimplemented(); }
+  abstract viewToModelUpdate(newValue: any): void;
 }