diff --git a/rx.js/rx.async-tests.ts b/rx.js/rx.async-tests.ts
index 9403c7517..9c3bce516 100644
--- a/rx.js/rx.async-tests.ts
+++ b/rx.js/rx.async-tests.ts
@@ -81,4 +81,8 @@ module Rx.Tests.Async {
 		ps = p.then(x=> "");
 		ps = p.then(x=> ps);
 	}
+
+	function startAsync() {
+		var o: Rx.Observable<string> = Rx.Observable.startAsync(() => <Rx.IPromise<string>>null);
+	}
 }
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