Upgrading Lumen from 5.3 to 5.4 breaks routing - requires additional prefix

I am following the upgrade guide to get a Lumen app onto the latest version. The step up to 5.4 breaks routing in the following way.

There is a route at /oauth/test.

It now results in a 404 (was fine on 5.3): http://testcase.local/oauth/test

It works if double-nesting the route, as follows:

http://testcase.local/oauth/oauth/test

It is slightly more complex in that the frontend (single page JS) of the application is served behind apache, and the routes that are backend-based are symlinked in. However, apache is configured appropriately (FollowSymLinks) and the configuration worked fine in 5.3.

The routes list out correctly in php artisan route:list

What has changed in 5.4 to break this and how can I fix it?

Edit: The cause is this commit to Lumen.

So something in the way symfony/http-foundation processes symlink-based paths breaks for this use case.

Workaround was to change the logic in the below method:

class Application extends \Laravel\Lumen\Application
{
    /**
     * This override fixes our routing problem
     * https://stackoverflow.com/questions/49048199/upgrading-lumen-from-5-3-to-5-4-breaks-routing-requires-additional-prefix
     *
     * Parse the incoming request and return the method and path info.
     *
     * @param  \Symfony\Component\HttpFoundation\Request|null  $request
     * @return array
     */
    protected function parseIncomingRequest($request)
    {
        if (! $request) {
            $request = Request::capture();
        }

        $this->instance(Request::class, $this->prepareRequest($request));

        // need the base url as well as the pathinfo when coming from symlinks
        return [$request->getMethod(), '/'.trim($request->getBaseUrl() . $request->getPathInfo(), '/')];
    }
}