Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.161
diff -u -F^f -r1.161 form.inc
--- includes/form.inc	26 Nov 2006 22:35:20 -0000	1.161
+++ includes/form.inc	2 Dec 2006 11:40:49 -0000
@@ -1210,7 +1210,11 @@ function theme_checkbox($element) {
  *   A themed HTML string representing the checkbox set.
  */
 function theme_checkboxes($element) {
-  $element['#children'] = '<div class="form-checkboxes">'. $element['#children'] .'</div>';
+  $class = 'form-checkboxes';
+  if (isset($element['#attributes']['class'])) {
+    $class .= ' '. $element['#attributes']['class'];
+  }
+  $element['#children'] = '<div class="'. $class .'">'. $element['#children'] .'</div>';
   if ($element['#title'] || $element['#description']) {
     unset($element['#id']);
     return theme('form_element', $element, $element['#children']);