diff --git a/index.d.ts b/index.d.ts
index 83d72ba..a5b4024 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -152,6 +152,6 @@ declare namespace koaBody {
     }
 }
 
-declare function koaBody (options?: koaBody.IKoaBodyOptions): Koa.Middleware;
+declare function koaBody (options?: koaBody.IKoaBodyOptions): Koa.Middleware<{}, {}>;
 
 export = koaBody;