diff --git a/types/cors/cors-tests.ts b/types/cors/cors-tests.ts
index 83975549c7..ed4cd77213 100644
--- a/types/cors/cors-tests.ts
+++ b/types/cors/cors-tests.ts
@@ -47,4 +47,11 @@ app.use(cors({
         }
     }
 }));
+app.use(cors((req, cb) => {
+    if (req.query.trusted) {
+        cb(null, {origin: 'http://example.com', credentials: true});
+    } else {
+        cb(new Error('Not trusted'));
+    }
+}))
 
diff --git a/types/cors/index.d.ts b/types/cors/index.d.ts
index ab8ba2ed2d..bc7a567fc7 100644
--- a/types/cors/index.d.ts
+++ b/types/cors/index.d.ts
@@ -1,12 +1,9 @@
 // Type definitions for cors 2.8
 // Project: https://github.com/troygoode/node-cors/
-// Definitions by: Mihhail Lapushkin <https://github.com/mihhail-lapushkin/>
+// Definitions by: Alan Plum <https://github.com/pluma>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.2
 
-
-
-
 import express = require('express');
 
 type CustomOrigin = (
@@ -25,7 +22,13 @@ declare namespace e {
         preflightContinue?: boolean;
         optionsSuccessStatus?: number;
     }
+    type CorsOptionsDelegate = (
+        req: express.Request,
+        callback: (err: Error | null, options?: CorsOptions) => void
+    ) => void;
 }
 
-declare function e(options?: e.CorsOptions): express.RequestHandler;
+declare function e(
+    options?: e.CorsOptions | e.CorsOptionsDelegate
+): express.RequestHandler;
 export = e;