WooCommerce - Exclude child categories

<?php
  // exclude child categories
  // code goes in functions.php for your child theme
  // credit: http://stackoverflow.com/questions/26711013/hide-subcategories-products-in-the-macro-category-in-woocommerce
  add_filter('pre_get_posts', 'exclude_product_cat_children');
  function exclude_product_cat_children($wp_query) {
    if ( isset ( $wp_query->query_vars['product_cat'] ) && $wp_query->is_main_query()) {
      $wp_query->set('tax_query', array(
         array (
           'taxonomy' => 'product_cat',
           'field' => 'slug',
           'terms' => $wp_query->query_vars['product_cat'],
           'include_children' => false
         )
       )
    );
  }
}