WordPress Rewrite - Endpoint

Rewrite.php

<?php namespace Sneek;

class Rewrite 
{
    public function __construct()
    {
        add_filter( 'init', array($this, 'addProductSupportEndPoint'));
        add_filter( 'template_include', array($this, 'maybeLoadProductSupportTemplate'));
    }

    public function addProductSupportEndPoint()
    {
        add_rewrite_endpoint( 'support', EP_PERMALINK );
    }

    public function maybeLoadProductSupportTemplate( $template )
    {
        global $wp_query;

        if ( ! isset( $wp_query->query_vars['support'] ) or ! is_singular( 'product' ) )
        {
            return $template;
        }

        if ( ! empty( $wp_query->query_vars['support'] ) ) {
            $wp_query->set_404();
            status_header( 404 );
            return locate_template( '404.php' );
        }

        return locate_template( 'single-product-support.php' );
    }
}