diff --git a/types/cookie-session/cookie-session-tests.ts b/types/cookie-session/cookie-session-tests.ts
index 74b7cafc8f..e9beea5c06 100644
--- a/types/cookie-session/cookie-session-tests.ts
+++ b/types/cookie-session/cookie-session-tests.ts
@@ -2,6 +2,7 @@
 
 import express = require('express');
 import cookieSession = require('cookie-session');
+import Keygrip = require('keygrip');
 
 var app = express()
 
@@ -36,4 +37,15 @@ app2.use(cookieSession({
 // have a different value than the default.
 app2.use(function (req, res, next) {
   req.sessionOptions.maxAge = req.session['maxAge'] || req.sessionOptions.maxAge
-});
\ No newline at end of file
+});
+
+
+var app3 = express()
+
+app3.set('trust proxy', 1) // trust first proxy
+
+// a Keygrip object may be used instead of an array of keys.
+app3.use(cookieSession({
+  name: 'session',
+  keys: Keygrip(['key1', 'key2'])
+}));
\ No newline at end of file
diff --git a/types/cookie-session/index.d.ts b/types/cookie-session/index.d.ts
index af48860396..8166645b97 100644
--- a/types/cookie-session/index.d.ts
+++ b/types/cookie-session/index.d.ts
@@ -1,10 +1,11 @@
 // Type definitions for cookie-session 2.0
 // Project: https://github.com/expressjs/cookie-session
-// Definitions by: Borislav Zhivkov <https://github.com/borislavjivkov>
+// Definitions by: Borislav Zhivkov <https://github.com/borislavjivkov>, Jason Cordial <https://github.com/btomw>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
-// TypeScript Version: 2.2
+// TypeScript Version: 2.9
 
 /// <reference types="express" />
+/// <reference types="keygrip" />
 
 declare namespace Express {
     interface Request extends CookieSessionInterfaces.CookieSessionRequest {}
@@ -20,7 +21,7 @@ declare namespace CookieSessionInterfaces {
         /**
          * The list of keys to use to sign & verify cookie values. Set cookies are always signed with keys[0], while the other keys are valid for verification, allowing for key rotation.
          */
-        keys?: Array<string>;
+        keys?: Array<string> | import('keygrip');
 
         /**
          * A string which will be used as single key if keys is not provided.