form POST to same page, request method remains GET

I'm trying to post a form to the current page and process it there. To this end I addes a matched route to Routes.php:

PHP Code:

$routes->match(['get', 'post'], 'klanten/(:segment)', 'Klanten::bewerk/$1'); 


 I do not have a route set up that overwrites this route. Here is the full routes list:

PHP Code:

$routes->match(['get', 'post'], 'soorten/(:segment)', 'Soorten::index/$1');
$routes->match(['get', 'post'], 'deurbel/(:segment)/(:segment)', 'Deurbel::index/$1/$2');
$routes->get('klanten', 'Klanten::index');
$routes->post('klanten/toevoegen', 'Klanten::toevoegen');
$routes->match(['get', 'post'], 'klanten/(:segment)', 'Klanten::bewerk/$1');
$routes->get('/', 'Dashboard::index'); 


When I post the form somehow the request method keeps coming back as get instead of post... Here is my form HTML:

Code:

<form action="/klanten/<?= esc($klant['slug']) ?>/" method="post">
                <div class="row">
                    <div class="col-12">
                        <div class="form-group">
                            <label for="naam">Naam: </label>
                            <input type="text" class="form-control" name="naam" id="naam" value="<?= $klant['naam'] ?>">
                        </div>
                        <div class="form-group">
                            <label for="woonplaats">Woonplaats: </label>
                            <input type="text" class="form-control" name="woonplaats" id="woonplaats" value="<?= $klant['woonplaats'] ?>">
                        </div>
                    </div>
                </div>
                 <?php if(isset($validation)): ?>
                     <div class="row">
                        <div class="alert alert-danger" role="alert">
                            <?= $validation->listErrors() ?>
                        </div>
                     </div>
                    <?php endif;?>
                    <div class="row">
                        <div class="row">
                            <div class="col-12 col-sm-4">
                                <button type="submit" class="btn btn-success">Opslaan</button>
                            </div>
                        </div>
                    </div>
            </form>

As you can see, I do have the forms method as post. 
The debug bar does show the route is there:

Image doesn't work, here is the link: http://development.medicalcrossteam.nl/i...ns-get.png

By now I'm ready to smash my head against the wall, because I can't figure out what is going on here. I'm hopinh you guys can help me and prevent me from doing that