Vercel deployment issue 404: NOT_FOUND when using middleware on dynamic routes

Verify canary release

• I verified that the issue exists in Next.js canary release

Provide environment information

Operating System:
      Platform: win32
      Arch: x64
      Version: Windows 10 Home Single Language
    Binaries:
      Node: 16.13.2
      npm: N/A
      Yarn: N/A
      pnpm: N/A
    Relevant packages:
      next: 12.1.5-canary.1
      react: 18.0.0
      react-dom: 18.0.0

What browser are you using? (if relevant)

Microsoft Edge

How are you deploying your application? (if relevant)

Vercel

Describe the Bug

I am deploying my apps to Vercel. but got a 404 not found page when I have _middleware.ts on dynamic routes and when I’m visiting the dynamic routes.

It works fine in my local

My middleware just return the NextResponse,next() like this

import { NextResponse } from "next/server";

const middleware = () => {
  return NextResponse.next();
};

export default middleware;

Expected Behavior

• Page can be visited when deployed to Vercel without a 404 issue

To Reproduce

I created a small repository to reproduce

https://github.com/bryantobing12/try-next-middleware

To test. when visiting /test it’s returning 404 not found when deployed to vercel. Only happening in dynamic routes

i have this route /[customerSlug] https://try-next-middleware.vercel.app/test

It works fine When visiting static page

https://try-next-middleware.vercel.app/dashboard

[balazsorban44]

A fix has been released to canary, please test it out (npm i next@canary)

[github-actions[bot]]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.