Nelmio API doc: Documentation says my json objects are arrays, how to fix?

Question

I'm using Nelmio API docs to generate the documentation for my REST api using FOSRestBundle and JMSSerializer. The docs generated say my json objects are actually arrays. How do I make the documentation say my objects are objects?

I know under the hood, in php these fields are actually key-value associative arrays, but in the actual json they are objects and I'd like my documentation to reflect that.

Here is my code entity:

/**
 *
 * Class Facility
 * @package Company\Bundle\RestApiBundle\Entity
 *
 * @Serializer\XmlRoot("facility")
 *
 * @Hateoas\Relation("self", href = "expr('/facility/' ~ object.getId())")
 * @Hateoas\Relation(
 *     "units",
 *     embedded = "expr(object.getUnits())"
 * )
 * @Hateoas\Relation(
 *     "reviews",
 *     embedded = "expr(object.getReviews())"
 * )
 *
 */
class Facility
{
...
    /**
     * @var
     * @Serializer\Type("array")
     */
    protected $amenities;
...
}

controller:

/**
 * Resource describing the Facility object
 *
 * @ApiDoc(
 *   resource = true,
 *   resourceDescription="Operations on facilities.",
 *   description = "Facility object",
 *   output = "Company\Bundle\RestApiBundle\Entity\Facility",
 *   statusCodes = {
 *     200 = "Returned when successful",
 *     404 = "Returned when the resource is not found"
 *   }
 * )
 *
 * @param $id
 * @return \Symfony\Component\HttpFoundation\Response
 *
 * @Method("GET")
 * @Route("/{id}", name = "api_facility_get")
 */
public function getFacilityAction($id)
{