request.js is always returning the default locale

[memoday]

Environment
Next.js: 14.2.26

next-intl: 4.1.0

Problem
I followed the official next-intl documentation to set up i18n.
However, I noticed that requestLocale is always undefined inside getRequestConfig, even when I access routes like /en, /ko.
(Since it is undefined, it always return the default locale set inside the routing.js)

Here’s the relevant part of my code:

// i18n/request.js
import { getRequestConfig } from "next-intl/server";
import { hasLocale } from "next-intl";
import { routing } from "./routing";

export default getRequestConfig(async ({ requestLocale }) => {
  console.log("requested", requestLocale); // always undefined

  const locale = hasLocale(routing.locales, requestLocale)
    ? requestLocale
    : routing.defaultLocale;

  console.log("final locale", locale);

  return {
    locale,
    messages: (await import(`../../messages/${locale}.json`)).default,
  };
});


// Console output:
// requested undefined
// final locale ko

ko is my default locale.

Even when I access http://localhost:3000/en, requestLocale is still undefined.

Additional Info
In root layout.js, when Iconsole log the locale params, it returns well.

My middleware.js is set up exactly as shown in the next-intl documentation.

Question
How should I fix my request.js to make it work properly?

Thanks in advance for any help!