diff --git a/lib/lib.es5.d.ts b/lib/lib.es5.d.ts
index f359e519ab13e..431b69fc54aee 100644
--- a/lib/lib.es5.d.ts
+++ b/lib/lib.es5.d.ts
@@ -236,7 +236,7 @@ interface ObjectConstructor {
       * Returns the names of the enumerable properties and methods of an object.
       * @param o Object that contains the properties and methods. This can be an object that you created or an existing Document Object Model (DOM) object.
       */
-    keys(o: any): string[];
+    keys<A>(o: A): (keyof A)[];
 }
 
 /**