diff --git a/core/lib/Drupal/Core/Field/WidgetBase.php b/core/lib/Drupal/Core/Field/WidgetBase.php
index aa285e2..44fe57a 100644
--- a/core/lib/Drupal/Core/Field/WidgetBase.php
+++ b/core/lib/Drupal/Core/Field/WidgetBase.php
@@ -106,8 +106,8 @@ public function form(FieldItemListInterface $items, array &$form, FormStateInter
       $elements = $this->formMultipleElements($items, $form, $form_state);
     }
 
-    // Populate the 'array_parents' information in $form_state['field'] after
-    // the form is built, so that we catch changes in the form structure
+    // Populate the 'array_parents' information in $form_state->get('field')
+    // after the form is built, so that we catch changes in the form structure
     // performed in alter() hooks.
     $elements['#after_build'][] = array(get_class($this), 'afterBuild');
     $elements['#field_name'] = $field_name;
@@ -461,7 +461,7 @@ public static function setWidgetState(array $parents, $field_name, FormStateInte
    */
   protected static function getWidgetStateParents(array $parents, $field_name) {
     // Field processing data is placed at
-    // $form_state['field']['#parents'][...$parents...]['#fields'][$field_name],
+    // $form_state->get(['field', '#parents', ...$parents..., '#fields', $field_name]),
     // to avoid clashes between field names and $parents parts.
     return array_merge(array('field', '#parents'), $parents, array('#fields', $field_name));
   }