cakephp-upload won´t validate - php

Question

I´am using the plugin
https://github.com/josegonzalez/cakephp-upload
for image upload.
I won´t to disable adding post without uploaded image.
How to write validation to it?
class BlogContent extends AppModel
{
public $validate = array(
'title' => array(
'rule' => 'notEmpty',
'message' => 'Titulok musí byť zadaný'
),
'text' => array(
'rule' => 'notEmpty',
'required' => true,
'message' => 'Text musí byť zadaný'
),
'photo' => array(
'isUpload' => array(
'rule' => 'isFileUpload',
'required' => true,
'message' => 'Článok musí obsahovať obrázok',
'last' => false
),
'isCompletedUpload' => array(
'rule' => 'isCompletedUpload',
'message' => 'Obrázok nebol úspešne nahratý',
'last' => false
),
'tempDirExists' => array(
'rule' => 'tempDirExists',
'message' => 'Priečinok TEMP nie je dostupný',
'last' => false
),
...
If I use required=> true for isUpload, it will never validates. However if I not type it, it will validates without uploading image.
View code: admin_add.ctp
<div class="blogContents form">
<?php echo $this->Form->create('BlogContent', array('type' => 'file'));
echo $this->Form->input('title', array('label' => 'Titulok'));
echo $this->Form->input('text', array('class' => 'ckeditor', 'label' => ''));
echo $this->Form->input('image', array('label' => '', 'type' => 'file', 'accept' => 'image/*'));
echo $this->Html->link(__('Vybrať obrázok'), '#', array('class' => 'btn btn-default', 'id' => 'upload'));
echo _('<p>Zvolený obrázok:</p>');
echo $this->Html->div('filelist', '<p>Žiaden obrázok nebol zvolený</p>');
echo $this->Form->input('image_dir', array('type' => 'hidden'));
echo $this->Form->input('active', array('label' => 'Publikované'));
echo $this->Form->submit(__('Uložiť článok'), array('class' => 'btn btn-success')) ?>
</div>