I want to opt specific packages out of bundling.

The documentation says:

/** @type {import('next').NextConfig} */
const nextConfig = {
  serverExternalPackages: ['package-name'],
}
 
module.exports = nextConfig

but the compiler says otherwise:

⚠ Invalid next.config.mjs options detected: 
⚠     Unrecognized key(s) in object: 'serverExternalPackages'
⚠ See more info here: https://nextjs.org/docs/messages/invalid-next-config

I did try this, of course:

/** @type {import('next').NextConfig} */
const nextConfig = {
  serverExternalPackages: ['package-name'],
}
 
module.exports = nextConfig

but the compiler immediately throws an error.