I'm using laravel 5.4 to make a custom form validation. But why is the custom error message isn't displayed?

Validator::extend('myCustomeValidator', function ($attribute, $value, $parameters, $validator) {
    //some code here
    return false;
});

return Validator::make($data, [
    'myField' => 'myCustomeValidator',
]);

and added the following to the file : ressources\lang\en\validation.php as the documentation advises:

'custom' => [
    'myField' => [
        'myCustomeValidator' => 'You made an error.',
    ],
],

The error is correctly triggered but instead of my custom error message, I get this:

validation.my_custome_validator

What am I missing?