Argument 1 passed to Gregwar\CaptchaBundle\Type\CaptchaType::__construct() must implement interface SessionInterface

[tzack1]

Error: Argument 1 passed to Gregwar\CaptchaBundle\Type\CaptchaType::__construct() must implement interface Symfony\Component\HttpFoundation\Session\SessionInterface

Symfony 2.8.16:

bundle registered:
$bundles = array(
// ...
new Gregwar\CaptchaBundle\GregwarCaptchaBundle(),
);
configured:
gregwar_captcha: ~

$builder->add('captcha', 'CaptchaType::class');

composer.json:
"gregwar/captcha-bundle": "^2.0"

Am I missing any steps?