diff --git a/rx.js/rx.async-tests.ts b/rx.js/rx.async-tests.ts
index b71f8bd77..9403c7517 100644
--- a/rx.js/rx.async-tests.ts
+++ b/rx.js/rx.async-tests.ts
@@ -66,8 +66,12 @@ module Rx.Tests.Async {
 			new<T>(resolver: (resolvePromise: (value: T)=> void, rejectPromise: (reason: any)=> void)=> void): Rx.IPromise<T>;
 		};
 
+		Rx.config.Promise = promiseImpl;
+
 		var p: IPromise<number> = obsNum.toPromise(promiseImpl);
 
+		p = obsNum.toPromise();
+
 		p = p.then(x=> x);
 		p = p.then(x=> p);
 		p = p.then(undefined, reason=> 10);
diff --git a/rx.js/rx.d.ts b/rx.js/rx.d.ts
index 2b9a68dc9..d0dc1eda3 100644
--- a/rx.js/rx.d.ts
+++ b/rx.js/rx.d.ts
@@ -47,7 +47,7 @@ declare module Rx {
 	}
 
 	export module config {
-		export var Promise: { new <T>(resolve: (value: T) => void, reject: (reason: any) => void): IPromise<T>; };
+		export var Promise: { new <T>(resolver: (resolvePromise: (value: T) => void, rejectPromise: (reason: any) => void) => void): IPromise<T>; };
 	}
 
 	export interface IDisposable {