Wordpress: disables singulars for custom post types

cpt.php

/**
 * Disables singular post view for custom post types. Throws 404 error instead.
 * @param $query
 */
function my_prefix_disable_singulars()
{
    global $wp_query;

    $disabled_singulars = array('post-type-1', 'post-type-2', 'post-type-3');

    if (($wp_query->is_main_query() && $wp_query->is_singular && !empty($wp_query->query['post_type']) && in_array($wp_query->query['post_type'], $disabled_singulars))) {
        $wp_query->set_404();
        status_header(404);
        require __DIR__ . '/path/to/404/template.php';
        exit();
    }
}

add_action('wp', 'my_prefix_disable_singulars');