How do i fallback to a legacy system with nextjs?

I’m using NextJS and I’d like to fall back to my legacy system. How do I do that?

in layer0.config.js

module.exports = {
  connector: '@layer0/next', 
    legacy: {
        domainOrIp: process.env.LEGACY_WWW_BACKEND,
        hostHeader: process.env.LEGACY_WWW_BACKEND_HOST_HEADER,
    },
  },
};

in routes.js

module.exports = new Router()
  .match('/service-worker.js', ({ serviceWorker }) => {
    return serviceWorker('.next/static/service-worker.js')
  })
  .use(nextRoutes)
  .fallback(({ proxy }) => proxy('legacy'))

Documented here:
https://docs.layer0.co/guides/next#section_nextroutes_middleware