diff --git a/angularjs/angular.d.ts b/angularjs/angular.d.ts
index fb452fa273..3e0185c35d 100644
--- a/angularjs/angular.d.ts
+++ b/angularjs/angular.d.ts
@@ -119,6 +119,7 @@ declare module ng {
     ///////////////////////////////////////////////////////////////////////////
     interface IAttributes {
         $set(name: string, value: any): void;
+        $observe(name: string, fn:(value?:any)=>any):void;
         $attr: any;
     }