Lumen Upgrade 5.5.* Broken! Call to a member function run() on integer (index.php)

Hello,

I am trying to upgrade my lumen installation to 5.5. I have followed instructions on the upgrade guide https://lumen.laravel.com/docs/5.5/upgrade#upgrade-5.5.0

But after doing so I am getting error.

(1/1) FatalThrowableError

Call to a member function run() on integer
in index.php (line 28)

Here is my index.php

<?php

/*
|--------------------------------------------------------------------------
| Create The Application
|--------------------------------------------------------------------------
|
| First we need to get an application instance. This creates an instance
| of the application / container and bootstraps the application so it
| is ready to receive HTTP / Console requests from the environment.
|
*/

$app = require __DIR__.'/../bootstrap/app.php';

/*
|--------------------------------------------------------------------------
| Run The Application
|--------------------------------------------------------------------------
|
| Once we have the application, we can handle the incoming request
| through the kernel, and send the associated response back to
| the client's browser allowing them to enjoy the creative
| and wonderful application we have prepared for them.
|
*/

$app->run();

var_dump($app) shows 1