add_filter('rewrite_rules_array', 'rewrite_rules_array_custom');
    function rewrite_rules_array_custom($_rules){
        $rules = array();
        foreach($_rules as $key=>$rule){
            if (strpos($key, 'artists') !== false){
                if (!isset($rulesSetted)){
                    $rulesSetted = true;
                    $rules['artists/([^/]+).html?$'] = 'index.php?post_type=artists&artists=$matches[2]&paged=1';
                }
            } else {
                $rules[$key] = $rule;
            }

        }
        return $rules;
    }