Why are /de-DE routes with i18n Next.js returning a 500?

Here’s the site: TaxPal - Accounting made simple for small businesses

Removing /de-DE from the url works fine

It seems to work fine in local dev with ntl dev but when I push changes to publish it doesn’t seem to capture the /de-DE routes

Here’s my next.config.js

/** @type {import('next').NextConfig} */

module.exports = {
  reactStrictMode: true,
  swcMinify: true,
  i18n: {
    locales: ['en-US', 'de-DE'],
    defaultLocale: 'en-US',
  experimental: {
    newNextLinkBehavior: true,
    scrollRestoration: true,

Here’s package.json

  "name": "tailwindui-salient",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "dev": "next dev",
    "build": "next build",
    "start": "next start",
    "lint": "next lint"
  "browserslist": "defaults, not ie <= 11",
  "dependencies": {
    "@headlessui/react": "^1.7.2",
    "@heroicons/react": "^2.0.11",
    "@netlify/next": "^1.3.1",
    "@tailwindcss/forms": "^0.5.3",
    "autoprefixer": "^10.4.12",
    "clsx": "^1.2.1",
    "contentful": "^9.2.5",
    "cookies-next": "^2.1.1",
    "focus-visible": "^5.2.0",
    "next": "^12.3.2",
    "postcss-focus-visible": "^6.0.4",
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "remark": "^14.0.2",
    "remark-html": "^15.0.1",
    "tailwindcss": "^3.1.8"
  "devDependencies": {
    "@netlify/plugin-lighthouse": "^3.7.1",
    "@types/node": "18.8.2",
    "@types/react": "18.0.21",
    "eslint": "8.19.0",
    "eslint-config-next": "12.2.5",
    "prettier": "^2.7.1",
    "prettier-plugin-tailwindcss": "^0.1.13"

Hey Mike,

Have you tried the languagecode de without the country code? Let us know how it goes.

Hey @mikec,

Are you using any Middleware by any chance? If yes, could you share its source code?

@hrishikesh I was! Removing middleware did the trick. i18n now works.

To circle back to this, it has now been fixed and should be available in the current latest version of the Next.js runtime.