diff --git a/express-serve-static-core/express-serve-static-core.d.ts b/express-serve-static-core/express-serve-static-core.d.ts
index 8bb4863c6..70817018a 100644
--- a/express-serve-static-core/express-serve-static-core.d.ts
+++ b/express-serve-static-core/express-serve-static-core.d.ts
@@ -783,8 +783,7 @@ declare module "express-serve-static-core" {
     }
 
     interface NextFunction {
-        (): void;
-        (err: any): void;
+        (err?: any): void;
     }
 
     interface ErrorRequestHandler {
diff --git a/express/express-tests.ts b/express/express-tests.ts
index d344dc6eb..11f8fd44f 100644
--- a/express/express-tests.ts
+++ b/express/express-tests.ts
@@ -68,3 +68,6 @@ app.use((req, res, next) => {
 app.use(router);
 
 app.listen(3000);
+
+const next: express.NextFunction = () => {};
+const nextWithArgument: express.NextFunction = (err: any) => {};