diff --git a/types/koa-session/index.d.ts b/types/koa-session/index.d.ts
index bd31a897e3..ae5e2c48fa 100644
--- a/types/koa-session/index.d.ts
+++ b/types/koa-session/index.d.ts
@@ -59,7 +59,7 @@ declare namespace session {
         /**
          * Hook: valid session value before use it
          */
-        valid(...rest: any[]): void;
+        valid?(...rest: any[]): void;
 
         /**
          * Hook: before save session
diff --git a/types/koa-session/koa-session-tests.ts b/types/koa-session/koa-session-tests.ts
index 266cb4b98b..ef3ddc6a09 100644
--- a/types/koa-session/koa-session-tests.ts
+++ b/types/koa-session/koa-session-tests.ts
@@ -1,5 +1,5 @@
 import * as Koa from 'koa';
-import session = require('koa-session');
+import * as session from 'koa-session';
 
 const app = new Koa();