diff --git a/core/modules/options/lib/Drupal/options/Plugin/Field/FieldWidget/OptionsWidgetBase.php b/core/modules/options/lib/Drupal/options/Plugin/Field/FieldWidget/OptionsWidgetBase.php
index 98f0d2e..e5801d9 100644
--- a/core/modules/options/lib/Drupal/options/Plugin/Field/FieldWidget/OptionsWidgetBase.php
+++ b/core/modules/options/lib/Drupal/options/Plugin/Field/FieldWidget/OptionsWidgetBase.php
@@ -82,12 +82,13 @@ public static function validateElement(array $element, array &$form_state) {
       \Drupal::formBuilder()->setError($element, $form_state, t('!name field is required.', array('!name' => $element['#title'])));
     }
 
-    // The $element generated by the various formElement() implementations can
-    // return a string if the field is single-valued (radios / select in single
-    // mode).
-    if (!is_array($element['#value'])) {
-      \Drupal::formBuilder()->setValue($element, array($element['#value']), $form_state);
+    if (is_array($element['#value'])) {
+      $values = array_values($element['#value']);
     }
+    else {
+      $values = array($element['#value']);
+    }
+    \Drupal::formBuilder()->setValue($element, $values, $form_state);
   }
 
   /**