Fatal error: Class 'Phalcon\Validation\Validator\File'

I'm trying to validate a File field (image upload). But I am getting the error:

  Fatal error: Class 'Phalcon\Validation\Validator\File' not found in CreateSnapForm.php on line 70

Here are the namespace in CreateSnapForm.php. I've marked line 70:

private function imageField()
{
    $image = new File('image');

    # Line 70 is the line below ...
    $image->addValidator(new FileValidator([
        'maxSize'       => '2M',
        'messageSize'   => 'Your image exceeds the max filesize (:max).',
        'allowedTypes'  => ['image/jpeg', 'image/png'],
        'messageType'   => 'Your image is not a valid image file.',
    ]));

    $this->add($image);
}

Line 70 is the above.

use Phalcon\Forms\Form;
use Phalcon\Forms\Element\Text;
use Phalcon\Forms\Element\Select;
use Phalcon\Forms\Element\Textarea;
use Phalcon\Forms\Element\Check;
use Phalcon\Forms\Element\Image;
use Phalcon\Forms\Element\File;
use Phalcon\Forms\Element\Hidden;
use Phalcon\Forms\Element\Submit;
use Phalcon\Validation\Validator\PresenceOf;
use Phalcon\Validation\Validator\StringLength;
use Phalcon\Validation\Validator\InclusionIn;
use Phalcon\Validation\Validator\Identical;
use Phalcon\Validation\Validator\File as FileValidator;

I have tried hard coding the namespace but I still get the same error.

$image->addValidator(new Phalcon\Validation\Validator\File([
        'maxSize'       => '2M',
        'messageSize'   => 'Your image exceeds the max filesize (:max).',
        'allowedTypes'  => ['image/jpeg', 'image/png'],
        'messageType'   => 'Your image is not a valid image file.',
]));

Any idea what's happening?