WooCommerce - Set default shop order to random

<?php
  // WooCommerce - Set default shop order to random
  add_filter('woocommerce_get_catalog_ordering_args', 'set_default_sort_order');
  function set_default_sort_order($args) {
     // see if the user has selected a sort order, if so, do not set the order
     if ( !isset( $_GET['orderby'] ) ) {
       $args['orderby'] = 'rand';
     }
    return ($args);
  }