diff --git a/index.d.ts b/index.d.ts
index da2c998..7ee3bd4 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,12 +1,27 @@
 /// <reference no-default-lib="true"/>
 /// <reference path="./lib.fetch.d.ts" />
 
-type _fetch = typeof fetch
-type _Response = Response
-type _Request = Request
+declare function _fetch(input: RequestInfo, init?: RequestInit): Promise<Response>;
+
+declare var _Request: {
+  prototype: Request;
+  new(input: RequestInfo, init?: RequestInit): Request;
+};
+
+declare var _Response: {
+  prototype: Response;
+  new(body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
+  redirect(url: string, status?: number): Response;
+};
+
+declare var _Headers: {
+  prototype: Headers;
+  new(init?: HeadersInit): Headers;
+};
+
 type _RequestInfo = RequestInfo
 type _RequestInit = RequestInit
-type _Headers = Headers
 
 export {
   _fetch as fetch,