Zend formBuilder raising exception on checkbox rendering

I'm trying to use Zend Framework 2 formBuilder with annotations in my model, but it's throwing an exception when trying to render a checkbox:

Model property annotation:

/**
 * @var boolean $Content
 *
 * @ORM\Column(name="Content", type="boolean", nullable=false)
 * @Annotation\Attributes({"type":"checkbox"})
 * @Annotation\Options({"label":"Value:"})
 * @Annotation\AllowEmpty({"true"})
 * @Annotation\Filter({"name":"Boolean"})
 */
protected $Content = true;

HTML from form template (phtml)

        <div id="Content">
            <?= $form->get('Content)->getLabel(); ?>
            <?= $this->formCheckbox($form->get('Content)); ?>
        </div>

When it tries to run the formCheckbox, it is throwing

 PHP Fatal error:  Uncaught exception 'Zend\\Form\\Exception\\InvalidArgumentException' with message 'Zend\\Form\\View\\Helper\\FormCheckbox::render requires that the element is of type Zend\\Form\\Element\\Checkbox' in /media/finaoweb/doctrine-test/vendor/zendframework/zend-form/src/View/Helper/FormCheckbox.php:29
Stack trace:
#0 /media/finaoweb/doctrine-test/vendor/zendframework/zend-form/src/View/Helper/FormInput.php(101): Zend\\Form\\View\\Helper\\FormCheckbox->render(Object(Zend\\Form\\Element))
#1 [internal function]: Zend\\Form\\View\\Helper\\FormInput->__invoke(Object(Zend\\Form\\Element))
#2 /media/finaoweb/doctrine-test/vendor/zendframework/zend-view/src/Renderer/PhpRenderer.php(393): call_user_func_array(Object(Zend\\Form\\View\\Helper\\FormCheckbox), Array)
#3 /media/finaoweb/doctrine-test/module/Application/view/application/itemoption/edititemoption.phtml(34): Zend\\View\\Renderer\\PhpRenderer->__call('formCheckbox', Array)

Looking at the stack trace before the formCheckbox() call, I can see the element attributes including 'type => "checkbox"'

I have even tried changing 'checkbox' to \Zend\Form\Element\Checkbox and Zend\\Form\\Element\\Checkbox with no luck.

Any help is appreciated.