diff --git a/rx.js/rx.js.aggregates.d.ts b/rx.js/rx.js.aggregates.d.ts
index 36b87612e..fcc368461 100644
--- a/rx.js/rx.js.aggregates.d.ts
+++ b/rx.js/rx.js.aggregates.d.ts
@@ -11,6 +11,9 @@ declare module Rx {
 		aggregate(accumulator: (acc: T, value: T) => T): Observable<T>;
 		aggregate<TAcc>(seed: TAcc, accumulator: (acc: TAcc, value: T) => TAcc): Observable<TAcc>;
 
+		reduce(accumulator: (acc: T, value: T) => T): Observable<T>;
+		reduce<TAcc>(accumulator: (acc: TAcc, value: T) => TAcc, seed: TAcc): Observable<TAcc>;		// TS0.9.5: won't work https://typescript.codeplex.com/discussions/471751
+
 		any(predicate?: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): Observable<boolean>;
 		some(predicate?: (value: T, index: number, source: Observable<T>) => boolean, thisArg?: any): Observable<boolean>;	// alias for any