diff --git a/ui/ui.core.inc b/ui/ui.core.inc
index 70d75a9..6d6b648 100644
--- a/ui/ui.core.inc
+++ b/ui/ui.core.inc
@@ -582,7 +582,7 @@ class RulesPluginUI extends FacesExtender implements RulesPluginUIInterface {
       usort($form_values['vars']['items'], 'rules_element_sort_helper');
       foreach ($form_values['vars']['items'] as $item) {
         if ($item['type'] && $item['name'] && $item['label']) {
-          $vars[$item['name']] = array('label' => $item['label'], 'type' => $item['type']);
+          $vars[$item['name']] = array('label' => $item['label'], 'type' => $item['type'], 'allow null' => empty($item['required']));
           if (!$item['usage'][0]) {
             $vars[$item['name']]['parameter'] = FALSE;
           }
@@ -637,7 +637,11 @@ class RulesPluginUI extends FacesExtender implements RulesPluginUIInterface {
       '#default_value' => $name,
       '#element_validate' => array('rules_ui_element_machine_name_validate'),
     );
-
+    $form['required'] = array(
+      '#type' => 'checkbox',
+      '#default_value' => !isset($info['allow null']) || empty($info['allow null']),
+    );
+
     $usage[0] = !isset($info['parameter']) || $info['parameter'] ? 1 : 0;
     $usage[1] = $provided ? 1 : 0;
 
diff --git a/ui/ui.theme.inc b/ui/ui.theme.inc
index 42bf6e8..cad6245 100755
--- a/ui/ui.theme.inc
+++ b/ui/ui.theme.inc
@@ -64,7 +64,7 @@ function theme_rules_ui_variable_form($variables) {
   $elements = $variables['element'];
 
   $table['#theme'] = 'table';
-  $table['#header'] = array(t('Data type'), t('Label'), t('Machine name'), t('Usage'), array('data' => t('Weight'), 'class' => array('tabledrag-hide')));
+  $table['#header'] = array(t('Data type'), t('Label'), t('Machine name'), t('Required'), t('Usage'), array('data' => t('Weight'), 'class' => array('tabledrag-hide')));
   $table['#attributes']['id'] = 'rules-' . drupal_html_id($elements['#title']) . '-id';
 
   foreach (element_children($elements['items']) as $key) {
@@ -76,6 +76,7 @@ function theme_rules_ui_variable_form($variables) {
     $row[] = array('data' => $element['type']);
     $row[] = array('data' => $element['label']);
     $row[] = array('data' => $element['name']);
+    $row[] = array('data' => $element['required']);
     $row[] = array('data' => $element['usage']);
     $row[] = array('data' => $element['weight']);
     $row = array('data' => $row) + $element['#attributes'];