Zend Framework 2. ZfcUser. Authentication error with right email/pass when i added new element in login form

I got authentication error with right email/pass of registered user when i added new element in login form in ZfcUser.

I added new element in bootstrap function with this lines:

<?php

namespace SystemUser;

use Zend\Mvc\ModuleRouteListener;
use Zend\Mvc\MvcEvent;

public function onBootstrap($e)
{
    $events = $e->getApplication()->getEventManager()->getSharedManager();
    $sharedEvents->attach('ZfcUser\Form\Login',
        'init',
        function($e)
        {
            // @var $form \ZfcUser\Form\Login
            $form = $e->getTarget();

            // Configure email input
            $form->get('identity')
                ->setAttribute('placeholder', 'Your email')
                ->setAttribute('class', 'text-input')
                ->setAttribute('title', 'Your email');

            // Configure password input
            $form->get('credential')
                ->setAttribute('placeholder', 'Your password')
                ->setAttribute('class', 'text-input')
                ->setAttribute('title', 'Your password');

            // Configure submit button
            $form->get('submit')
                ->setAttribute('class', 'btn btn-primary submit');

            // Add field "Keep me signed in."
            $form->add(
                array(
                    'type' => 'Zend\Form\Element\Checkbox',
                    'name' => 'keep_signed_in',
                    'options' => array(
                        'label' => 'Keep me signed in.',
                        'use_hidden_Element' => true,
                        'checked_value' => '1',
                        'unchecked_value' => '0'
                    ),
                    'attributes' => array(
                        'id' => 'keep_signed_in',
                    ),
                )
            );

        }
    );

}

But with new element 'keep_signed_in' login form allways returns error "Authentication failed. Please try again."

Please help. What I must to do for dropping this error with real auth params?

Thank you, guys!

I find out solution! :)

I forgot specify filter for this checkbox with required=false:

$sharedEvents->attach('ZfcUser\Form\LoginFilter', 'init', function($e) {
        // @var $form \ZfcUser\Form\LoginFilter
        $filter = $e->getTarget();

        // Custom field keep_signed_in
        $filter->add(array(
                'name'       => 'keep_signed_in',
                'required'   => false,
            )
        );

    }
);