public function doBuild()
    {
        $output = parent::build();
        if ($this->form && $this->form->status['submitted'] && !$this->props['isValid']) {
            // did not validate -> add hidden field
            $noticeName = $this->attribs['name'].'_notice';
            $this->debug->warn('buildControl', $this->form->buildControl);
            $output .= $this->form->buildControl->build(array(
                'type' => 'hidden',
                'name' => $noticeName,
                'value' => $this->val(),
            ));
        }
        return $output;
    }