diff --git a/packages/next/build/webpack/loaders/next-middleware-loader.ts b/packages/next/build/webpack/loaders/next-middleware-loader.ts
index cccfbd4cc0b2b..c93346f5b381e 100644
--- a/packages/next/build/webpack/loaders/next-middleware-loader.ts
+++ b/packages/next/build/webpack/loaders/next-middleware-loader.ts
@@ -15,7 +15,7 @@ export default function middlewareLoader(this: any) {
   }
 
   return `
-        import { adapter } from 'next/dist/server/web/adapter'
+        import { adapter, blockUnallowedResponse } from 'next/dist/server/web/adapter'
 
         // The condition is true when the "process" module is provided
         if (process !== global.process) {
@@ -32,11 +32,11 @@ export default function middlewareLoader(this: any) {
         }
 
         export default function (opts) {
-          return adapter({
+          return blockUnallowedResponse(adapter({
               ...opts,
               page: ${JSON.stringify(page)},
               handler,
-          })
+          }))
         }
     `
 }
diff --git a/packages/next/server/web/adapter.ts b/packages/next/server/web/adapter.ts
index a6eb6da2f4f08..053f3f7fe00c9 100644
--- a/packages/next/server/web/adapter.ts
+++ b/packages/next/server/web/adapter.ts
@@ -9,12 +9,7 @@ import { DeprecationError } from './error'
 import { fromNodeHeaders } from './utils'
 import { NextFetchEvent } from './spec-extension/fetch-event'
 import { NextRequest } from './spec-extension/request'
-import {
-  NextResponse,
-  RedirectHeader,
-  RewriteHeader,
-  NextMiddlewareHeader,
-} from './spec-extension/response'
+import { NextResponse, RedirectHeader } from './spec-extension/response'
 import { waitUntilSymbol } from './spec-compliant/fetch-event'
 
 export async function adapter(params: {
@@ -39,25 +34,32 @@ export async function adapter(params: {
   const event = new NextFetchEvent({ request, page: params.page })
   const response = await params.handler(request, event)
 
-  const error = isAllowed(response)
-    ? null
-    : new Response(
-        JSON.stringify({
-          message: `A middleware can not alter response's body. Learn more: https://nextjs.org/docs/messages/returning-response-body-in-_middleware`,
-        }),
-        {
-          status: 500,
-          statusText: 'Internal Server Error',
-          headers: { 'content-type': 'application/json' },
-        }
-      )
-
   return {
-    response: error || response || NextResponse.next(),
+    response: response || NextResponse.next(),
     waitUntil: Promise.all(event[waitUntilSymbol]),
   }
 }
 
+export function blockUnallowedResponse(
+  promise: Promise<FetchEventResult>
+): Promise<FetchEventResult> {
+  return promise.then((result) => ({
+    ...result,
+    response: isAllowed(result.response)
+      ? result.response
+      : new Response(
+          JSON.stringify({
+            message: `A middleware can not alter response's body. Learn more: https://nextjs.org/docs/messages/returning-response-body-in-_middleware`,
+          }),
+          {
+            status: 500,
+            statusText: 'Internal Server Error',
+            headers: { 'content-type': 'application/json' },
+          }
+        ),
+  }))
+}
+
 function isAllowed(response: NextMiddlewareResult): boolean {
   return (
     !response?.body || !response.body || response.headers.has(RedirectHeader)
diff --git a/packages/next/server/web/error.ts b/packages/next/server/web/error.ts
index ebe14d9f27d78..c659a570d9b50 100644
--- a/packages/next/server/web/error.ts
+++ b/packages/next/server/web/error.ts
@@ -3,7 +3,7 @@ export class DeprecationError extends Error {
     super(`The middleware "${page}" accepts an async API directly with the form:
   
   export function middleware(request, event) {
-    return new Response("Hello " + request.url)
+    return new NextResponse(null, { status: 403 })
   }
   
   Read more: https://nextjs.org/docs/messages/middleware-new-signature