diff --git a/types/wu/index.d.ts b/types/wu/index.d.ts
index 3d44b5140f..08a1b9f19a 100644
--- a/types/wu/index.d.ts
+++ b/types/wu/index.d.ts
@@ -30,7 +30,7 @@ declare namespace wu {
 	function enumerate<T>(iter: Iterable<T>): Iterable<[number, T]>;
 	function every<T>(fn: Filter<T>, iter: Iterable<T>): boolean;
 	function filter<T>(fn: Filter<T>, iter: Iterable<T>): WuIterable<T>;
-	function find<T>(fn: Filter<T>, iter: Iterable<T>): T;
+	function find<T>(fn: Filter<T>, iter: Iterable<T>): T | undefined;
 	function flatten(iter: Iterable<any>): WuIterable<any>;
 	function flatten(shallow: boolean, iter: Iterable<any>): WuIterable<any>;
 	function forEach<T>(fn: Consumer<T>, iter: Iterable<T>): void;
@@ -79,7 +79,7 @@ declare namespace wu {
 		enumerate(): Iterable<[number, T]>;
 		every(fn: Filter<T>): boolean;
 		filter(fn: Filter<T>): WuIterable<T>;
-		find(fn: Filter<T>): T;
+		find(fn: Filter<T>): T | undefined;
 		flatten(shallow?: boolean): WuIterable<any>;
 		forEach(fn: Consumer<T>): void;
 		has(t: T): boolean;