A facade root has not been set - Installing Passport

After installing Passport in a fresh install of Lumen, and registering the provider in app.php

$app->register(Laravel\Passport\PassportServiceProvider::class);

The following error is displayed on viewing the Laravel application:

RuntimeException in Facade.php line 218:

A facade root has not been set. in Facade.php line 218 at Facade::__callStatic('extend', array('passport', object(Closure))) in PassportServiceProvider.php line 233 at PassportServiceProvider->registerGuard() in PassportServiceProvider.php line 83 at PassportServiceProvider->register() in Application.php line 172 at Application->register(object(PassportServiceProvider)) in app.php line 84 at require('/www/flocrm/api/bootstrap/app.php') in index.php line 14