diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index 7382a18..6c11d23 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -1129,7 +1129,7 @@ protected function buttonWasClicked($element, FormStateInterface &$form_state) {
    * {@inheritdoc}
    */
   public function setValue($element, $value, FormStateInterface &$form_state) {
-    NestedArray::setValue($form_state['values'], $element['#parents'], $value, TRUE);
+    $form_state->setValue($element, $value);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Form/FormState.php b/core/lib/Drupal/Core/Form/FormState.php
index 8bba317..589010b 100644
--- a/core/lib/Drupal/Core/Form/FormState.php
+++ b/core/lib/Drupal/Core/Form/FormState.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Form;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Url;
 
 /**
@@ -462,6 +463,15 @@ public function getErrors() {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function setValue($element, $value) {
+    $values = &$this->get('values');
+    NestedArray::setValue($values, $element['#parents'], $value, TRUE);
+    return $this;
+  }
+
+  /**
    * Wraps drupal_set_message().
    *
    * @return array|null
diff --git a/core/lib/Drupal/Core/Form/FormStateInterface.php b/core/lib/Drupal/Core/Form/FormStateInterface.php
index 1748fca..28f3892 100644
--- a/core/lib/Drupal/Core/Form/FormStateInterface.php
+++ b/core/lib/Drupal/Core/Form/FormStateInterface.php
@@ -243,4 +243,33 @@ public function getErrors();
    */
   public function getError($element);
 
+  /**
+   * Changes submitted form values during form validation.
+   *
+   * Use this function to change the submitted value of a form element in a form
+   * validation function, so that the changed value persists in $form_state
+   * through to the submission handlers.
+   *
+   * Note that form validation functions are specified in the '#validate'
+   * component of the form array (the value of $form['#validate'] is an array of
+   * validation function names). If the form does not originate in your module,
+   * you can implement hook_form_FORM_ID_alter() to add a validation function
+   * to $form['#validate'].
+   *
+   * @param array $element
+   *   The form element that should have its value updated; in most cases you
+   *   can just pass in the element from the $form array, although the only
+   *   component that is actually used is '#parents'. If constructing yourself,
+   *   set $element['#parents'] to be an array giving the path through the form
+   *   array's keys to the element whose value you want to update. For instance,
+   *   if you want to update the value of $form['elem1']['elem2'], which should
+   *   be stored in $form_state['values']['elem1']['elem2'], you would set
+   *   $element['#parents'] = array('elem1','elem2').
+   * @param mixed $value
+   *   The new value for the form element.
+   *
+   * @return $this
+   */
+  public function setValue($element, $value);
+
 }
diff --git a/core/lib/Drupal/Core/Form/FormSubmitter.php b/core/lib/Drupal/Core/Form/FormSubmitter.php
index b212549..b3797d2 100644
--- a/core/lib/Drupal/Core/Form/FormSubmitter.php
+++ b/core/lib/Drupal/Core/Form/FormSubmitter.php
@@ -61,7 +61,7 @@ public function doSubmitForm(&$form, FormStateInterface &$form_state) {
     // \Drupal\Core\Form\FormBuilderInterface::submitForm).
     if ($batch = &$this->batchGet() && !isset($batch['current_set'])) {
       // Store $form_state information in the batch definition.
-      $batch['form_state'] = clone $form_state;
+      $batch['form_state'] = $form_state;
 
       $batch['progressive'] = !$form_state['programmed'];
       $response = batch_process();