diff --git a/gapi/gapi.d.ts b/gapi/gapi.d.ts
index 9a5f32eba6..9e4e603bb2 100644
--- a/gapi/gapi.d.ts
+++ b/gapi/gapi.d.ts
@@ -127,13 +127,21 @@ declare namespace gapi.auth {
 }
 
 declare namespace gapi.client {
+    /**
+    * Loads the client library interface to a particular API. If a callback is not provided, a promise is returned.
+    * @param name The name of the API to load.
+    * @param version The version of the API to load.
+    * @return promise The promise that get's resolved after the request is finished.
+    */
+    export function load(name: string, version: string): Promise<void>
+
     /**
     * Loads the client library interface to a particular API. The new API interface will be in the form gapi.client.api.collection.method.
     * @param name The name of the API to load.
     * @param version The version of the API to load
     * @param callback the function that is called once the API interface is loaded
     */
-    export function load(name: string, version: string, callback?: () => any): void;
+    export function load(name: string, version: string, callback: () => any): void;
     /**
     * Creates a HTTP request for making RESTful requests.
     * An object encapsulating the various arguments for this method.