Floating Textfield

Textfield added to user reg form is just floating out by itself.

Suggested:

<?php
    case 'register':
      if (og_reg_keys_visible_on_registration_form()) {

        $form['og_reg_key_field'] = array(
          '#type'        => 'fieldset',
          '#title'       => t('Group Code'),
        );
	
        $form['og_reg_key_field']['og_reg_key'] = array(
          '#type' => 'textfield',
          '#title' => t('Group registration key'),
          '#required' => og_reg_keys_required_for_registration(),
          '#description' => _og_reg_keys_help_text(),
          '#size' => 64,
        );
      }

      return $form;
      break;
?>