diff --git a/includes/form_bak.inc b/includes/form.inc
index df1b2f7..1f8ce9e 100644
--- a/includes/form_bak.inc
+++ b/includes/form.inc
@@ -1268,8 +1268,13 @@ function _form_validate(&$elements, &$form_state, $form_id = NULL) {
           $value = in_array($elements['#type'], array('checkboxes', 'tableselect')) ? array_keys($elements['#value']) : $elements['#value'];
           foreach ($value as $v) {
             if (!isset($options[$v])) {
-              form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
-              watchdog('form', 'Illegal choice %choice in !name element.', array('%choice' => $v, '!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
+              if ($elements['#type'] != 'radios') {
+                form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
+                watchdog('form', 'Illegal choice %choice in !name element.', array('%choice' => $v, '!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
+              }
+              else {
+                form_error($elements, $t('You must choose exactly one radio button.'));
+              }
             }
           }
         }