Zend Framework 2 Form, regex validation not being applied

I am using a stand alone Zend Form (I'm not using the full blown ZF2 MVC) and I have specified the following class to define the form:

use Zend\Form\Annotation;

/**
* @Annotation\Hydrator("Zend\Stdlib\Hydrator\ObjectProperty")
*/
class Student
{
    /**
     * @Annotation\Type("Zend\Form\Element\Text")
     * @Annotation\Options({"label":"Student code"})
     * @Annotations\Validator({"name":"Regex", "options":{"pattern":"/^[0-9]+$/"}})
     * @Annotation\Required({"required":"true"})
     */
    public $student_code;
}

This is the relevant code in my controller (simplified to only show the relevant parts)

public function createAction()
{
    $request = $this->getRequest();
    $student = new Student();
    $builder = new AnnotationBuilder();
    $form    = $builder->createForm($student);
    $form->bind($student);
    $form->setData($request->getPost());

    if ($form->isValid()) {
        var_dump($form->getPost());
    }
}

The problem is that when I submitt the form and with 'abc' as the value for student_code, the form is returning as valid. According to the Regex it should only accept numbers.

The required part works; the form is invalid if student_code is empty. My question is, what am I missing that the Regex is not working?

replace with:

 @Annotation\Validator({"name":"Regex", "options":{"pattern":"/^[0-9]+$/"}})

Note that I have removed the s at the end from @Annotation