diff --git a/core/lib/Drupal/Core/Form/FormInterface.php b/core/lib/Drupal/Core/Form/FormInterface.php
index 5789dd7..2d8864e 100644
--- a/core/lib/Drupal/Core/Form/FormInterface.php
+++ b/core/lib/Drupal/Core/Form/FormInterface.php
@@ -41,7 +41,7 @@ public function build(array $form, array &$form_state);
    * @param array $form_state
    *   An associative array containing the current state of the form.
    */
-  public function validate(array $form, array &$form_state);
+  public function validate(array &$form, array &$form_state);
 
   /**
    * Form submission handler.
@@ -51,6 +51,6 @@ public function validate(array $form, array &$form_state);
    * @param array $form_state
    *   An associative array containing the current state of the form.
    */
-  public function submit(array $form, array &$form_state);
+  public function submit(array &$form, array &$form_state);
 
 }
diff --git a/core/modules/block/lib/Drupal/block/BlockListController.php b/core/modules/block/lib/Drupal/block/BlockListController.php
index fb7b868..bde1ce7 100644
--- a/core/modules/block/lib/Drupal/block/BlockListController.php
+++ b/core/modules/block/lib/Drupal/block/BlockListController.php
@@ -192,7 +192,7 @@ public function build(array $form, array &$form_state) {
   /**
    * Implements \Drupal\Core\Form\FormInterface::validate().
    */
-  public function validate(array $form, array &$form_state) {
+  public function validate(array &$form, array &$form_state) {
     // No validation.
   }
 
@@ -201,7 +201,7 @@ public function validate(array $form, array &$form_state) {
    *
    * Form submission handler for the main block administration form.
    */
-  public function submit(array $form, array &$form_state) {
+  public function submit(array &$form, array &$form_state) {
     $entities = entity_load_multiple('block', array_keys($form_state['values']['blocks']));
     foreach ($entities as $entity_id => $entity) {
       $entity->set('weight', $form_state['values']['blocks'][$entity_id]['weight']);
diff --git a/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php b/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php
index f3666bc..12e6011 100644
--- a/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php
@@ -409,7 +409,7 @@ public function build(array $form, array &$form_state) {
   /**
    * Overrides \Drupal\field_ui\OverviewBase::submit().
    */
-  public function submit(array $form, array &$form_state) {
+  public function submit(array &$form, array &$form_state) {
     $form_values = $form_state['values'];
     $display = entity_get_display($this->entity_type, $this->bundle, $this->view_mode);
 
diff --git a/core/modules/field_ui/lib/Drupal/field_ui/FieldOverview.php b/core/modules/field_ui/lib/Drupal/field_ui/FieldOverview.php
index 426010e..d6a0046 100644
--- a/core/modules/field_ui/lib/Drupal/field_ui/FieldOverview.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/FieldOverview.php
@@ -422,7 +422,7 @@ public function build(array $form, array &$form_state) {
   /**
    * Overrides \Drupal\field_ui\OverviewBase::validate().
    */
-  public function validate(array $form, array &$form_state) {
+  public function validate(array &$form, array &$form_state) {
     $this->validateAddNew($form, $form_state);
     $this->validateAddExisting($form, $form_state);
   }
@@ -526,7 +526,7 @@ protected function validateAddExisting(array $form, array &$form_state) {
   /**
    * Overrides \Drupal\field_ui\OverviewBase::submit().
    */
-  public function submit(array $form, array &$form_state) {
+  public function submit(array &$form, array &$form_state) {
     $form_values = $form_state['values']['fields'];
 
     $bundle_settings = field_bundle_settings($this->entity_type, $this->bundle);
diff --git a/core/modules/field_ui/lib/Drupal/field_ui/OverviewBase.php b/core/modules/field_ui/lib/Drupal/field_ui/OverviewBase.php
index d44d2cf..9a37e67 100644
--- a/core/modules/field_ui/lib/Drupal/field_ui/OverviewBase.php
+++ b/core/modules/field_ui/lib/Drupal/field_ui/OverviewBase.php
@@ -63,13 +63,13 @@ public function __construct($entity_type, $bundle, $view_mode = NULL) {
   /**
    * Implements \Drupal\Core\Form\FormInterface::validate().
    */
-  public function validate(array $form, array &$form_state) {
+  public function validate(array &$form, array &$form_state) {
   }
 
   /**
    * Implements \Drupal\Core\Form\FormInterface::submit().
    */
-  public function submit(array $form, array &$form_state) {
+  public function submit(array &$form, array &$form_state) {
   }
 
   /**
diff --git a/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/FormTestObject.php b/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/FormTestObject.php
index 1498861..f3b0cf3 100644
--- a/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/FormTestObject.php
+++ b/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/FormTestObject.php
@@ -38,14 +38,14 @@ public function build(array $form, array &$form_state) {
   /**
    * Implements \Drupal\Core\Form\FormInterface::validate().
    */
-  public function validate(array $form, array &$form_state) {
+  public function validate(array &$form, array &$form_state) {
     drupal_set_message(t('The FormTestObject::validate() method was used for this form.'));
   }
 
   /**
    * Implements \Drupal\Core\Form\FormInterface::submit().
    */
-  public function submit(array $form, array &$form_state) {
+  public function submit(array &$form, array &$form_state) {
     drupal_set_message(t('The FormTestObject::submit() method was used for this form.'));
   }