Form macro triggers CSRF filter in Codeception

So I deciced to implement form macros and I ran into a strange problem. I've got no idea where exactly the problem is, maybe someone can help:

I store the form macros in app/formMacros.php and load that file in app/start/global.php:

require app_path() . '/formMacros.php';

That works, the file is loaded, I can define form macros and use them in my views. But if I define a form macro in that file, one of my functional tests goes red.

The test looks like this:

$I = new FunctionalTester($scenario);
$I->am('authenticated user');
$I->wantTo('access a route if authorized');

$I->enableRouteFilters();

$I->haveRecord('users', ['username' => 'foo', 'password' => Hash::make('bar'), 'role_id' => '1']);
$I->haveRecord('authorizations', ['route' => 'foobar', 'role_id' => '1', 'allowed' => '1']);

$I->amOnRoute('home');
$I->fillField("form#login-form input[name='username']", 'foo');
$I->fillField("form#login-form input[name='password']", 'bar');
$I->click("form#login-form input[type='submit']");

$I->amOnRoute('foobar');
$I->dontSeeElement('div.alert-danger');
$I->seeCurrentRouteIs('foobar');

and it fails with:

1) Failed to access a route if authorized in [...]
Couldn't click "form#login-form input[type='submit']":
Illuminate\Session\TokenMismatchException: 

Scenario Steps:
8. I click "form#login-form input[type='submit']"
7. I fill field "form#login-form input[name='password']","bar"
6. I fill field "form#login-form input[name='username']","foo"
5. I am on route "home"

So it seems the CSRF filter is triggered. I load them in my routes.php:

Route::when('*', 'csrf', array('post', 'put', 'delete'));

The Exception is only thrown if there are macro definitions in formMacros.php. It doesn't matter what names these macros have. Just putting this in it is enough:

Form::macro('someRandomMacroNameWhichIsProblablyNotUsedAnyWhere', function() {});

And it doesn't matter if I actually use any of these macros. The login form that triggers the exception doesn't use any form macros at all.

If I try to login in the browser, it works just fine, no exception is thrown.

So I'm a bit lost here. Has maybe anyone an idea?