diff --git a/kcors/index.d.ts b/kcors/index.d.ts
index e2618f63cb..e4e9e53fa6 100644
--- a/kcors/index.d.ts
+++ b/kcors/index.d.ts
@@ -1,6 +1,6 @@
 // Type definitions for kcors 2.2
 // Project: https://github.com/koajs/cors
-// Definitions by: Xavier Stouder <https://github.com/Xstoudi>
+// Definitions by: Xavier Stouder <https://github.com/Xstoudi>, Izayoi Ko <https://github.com/izayoiko>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 import * as Koa from "koa";
@@ -10,10 +10,10 @@ export = cors;
 
 declare namespace cors {
     interface Options {
-        origin?: (req: Koa.Request) => string | string;
+        origin?: ((req: Koa.Request) => string) | string;
         allowMethods?: string[] | string;
         exposeHeaders?: string[] | string;
-        allowHeaders: string[] | string;
+        allowHeaders?: string[] | string;
         maxAge?: number | string;
         credentials?: boolean;
         keepHeadersOnError?: boolean;