Alterar slug de um custom post type já registrado

functions.php

function change_post_type_slug() {
    $post_type_portfolio_object = get_post_type_object( 'portfolio' );
    $post_type_portfolio_object->rewrite['slug'] = 'produto';
  
    register_post_type( $post_type_object->name, $post_type_object );
}
add_action( 'init', 'change_post_type_slug', 20 );