diff --git a/webform.module b/webform.module
index d2bab7d..d671839 100644
--- a/webform.module
+++ b/webform.module
@@ -2257,7 +2257,7 @@ function _webform_client_form_validate($elements, &$form_state, $first_run = TRU
             }
           }
         }
-        elseif ($elements['#value'] !== '' && !isset($options[$elements['#value']])) {
+        elseif ($elements['#value'] !== FALSE && $elements['#value'] !== NULL && !isset($options[$elements['#value']])) {
           form_error($elements, t('An illegal choice has been detected. Please contact the site administrator.'));
           watchdog('form', 'Illegal choice %choice in %name element.', array('%choice' => $elements['#value'], '%name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
         }