diff --git a/src/Element/Registrants.php b/src/Element/Registrants.php
index b087c5a..6dbc0c1 100644
--- a/src/Element/Registrants.php
+++ b/src/Element/Registrants.php
@@ -186,7 +186,7 @@ public static function processIdentityElement(array &$element, FormStateInterfac
     $element['for_arity'] = [
       '#type' => 'radios',
       '#title' => t('This registration is for'),
-      '#options' => NULL,
+      '#options' => [],
       '#access' => $for_arity_any_arity && $change_it,
       '#attributes' => [
         'class' => ['for_arity'],