CI 4.18 -> 4.20 causes RouterException

Hi all,
I am upgrading from 4.18 to 4.20.
But now I receieve numerous RouterExceptions.
For example: Controller or its method is not found: \App\Controllers\Login::index
This is de routes.php rule:

PHP Code:

$routes->get('/beheer', 'Login::index'); 


And I do have a app/Controllers/Login.php file with an index() method in it.
I can't seem to find anything in the changelog what will cause this behaviour.