diff --git a/src/Router/Middleware.ts b/src/Router/Middleware.ts
index 1e27bfb..31f2047 100644
--- a/src/Router/Middleware.ts
+++ b/src/Router/Middleware.ts
@@ -13,7 +13,7 @@ import { Pattern } from './Pattern';
  * @param router The current router instance.
  * @return The Response instance.
  */
-export type MiddlewareBeforeHandler = (request: Request, response: Response, params: RequestParams, router: Router) => Response|Promise<Response>|void;
+export type MiddlewareBeforeHandler = (request: Request, response: Response, params: RequestParams, router: Router) => Response|void|Promise<Response|void>;
 
 /**
  * The signature of middleware handler to invoke after routing.
@@ -23,7 +23,7 @@ export type MiddlewareBeforeHandler = (request: Request, response: Response, par
  * @param router The current router instance.
  * @return The Response instance.
  */
-export type MiddlewareAfterHandler = (request: Readonly<Request>, response: Response, params: RequestParams, router: Router) => Response|Promise<Response>;
+export type MiddlewareAfterHandler = (request: Readonly<Request>, response: Response, params: RequestParams, router: Router) => Response|void|Promise<Response|void>;
 
 /**
  * The interface of a middleware rule.
diff --git a/src/Router/Route.ts b/src/Router/Route.ts
index f499006..2e0bbea 100644
--- a/src/Router/Route.ts
+++ b/src/Router/Route.ts
@@ -12,7 +12,7 @@ import { Pattern } from './Pattern';
  * @param router The current router instance.
  * @return The next Response instance.
  */
-export type NextHandler = (request: Request, response: Response, router: Router) => Response|Promise<Response>;
+export type NextHandler = (request: Request, response: Response, router: Router) => Response|void|Promise<Response|void>;
 
 /**
  * The signature of a Route handler method.
@@ -22,7 +22,7 @@ export type NextHandler = (request: Request, response: Response, router: Router)
  * @param router The current router instance.
  * @return The very same input Response instance or a new one.
  */
-export type RouteHandler = (request: Readonly<Request>, response: Readonly<Response>, next: NextHandler, router: Router) => Response|string|Promise<Response|string>;
+export type RouteHandler = (request: Readonly<Request>, response: Readonly<Response>, next: NextHandler, router: Router) => Response|string|void|Promise<Response|string|void>;
 
 /**
  * The interface of a route rule.
diff --git a/src/Router/Router.ts b/src/Router/Router.ts
index 3e00c7e..5f6677c 100644
--- a/src/Router/Router.ts
+++ b/src/Router/Router.ts
@@ -222,7 +222,7 @@ export class Router extends Factory.Emitter {
         );
 
         try {
-            response = await starter(request, response, this);
+            response = (await starter(request, response, this)) ?? response;
         } catch (error) {
             request.reject(error as Error);
             throw error;
diff --git a/src/Router/State.ts b/src/Router/State.ts
index 2254126..4f66e3c 100644
--- a/src/Router/State.ts
+++ b/src/Router/State.ts
@@ -9,6 +9,7 @@ export interface State {
     url: string;
     index: number;
     title: string;
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     store: any;
     request: Request;
     response?: Response;