diff --git a/core/lib/Drupal/Core/Entity/ContentEntityForm.php b/core/lib/Drupal/Core/Entity/ContentEntityForm.php
index 6980701..c892401 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityForm.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityForm.php
@@ -50,6 +50,11 @@ public static function create(ContainerInterface $container) {
    */
   public function form(array $form, FormStateInterface $form_state) {
     $form = parent::form($form, $form_state);
+
+    // Content entity forms are doing their own entity building so there's no
+    // need to use the parent one.
+    unset($form['#after_build']);
+
     $this->getFormDisplay($form_state)->buildForm($this->entity, $form, $form_state);
     // Allow modules to act before and after form language is updated.
     $form['#entity_builders']['update_form_langcode'] = [$this, 'updateFormLangcode'];
@@ -69,7 +74,7 @@ public function form(array $form, FormStateInterface $form_state) {
    * https://www.drupal.org/node/2015613.
    */
   public function validate(array $form, FormStateInterface $form_state) {
-    $entity = $this->entity;
+    $entity = $this->buildEntity($form, $form_state);
     $this->getFormDisplay($form_state)->validateFormValues($entity, $form, $form_state);
 
     // @todo Remove this.
@@ -80,6 +85,17 @@ public function validate(array $form, FormStateInterface $form_state) {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    parent::submitForm($form, $form_state);
+
+    // Remove button and internal Form API values from submitted values.
+    $form_state->cleanValues();
+    $this->entity = $this->buildEntity($form, $form_state);
+  }
+
+  /**
    * Initializes the form state and the entity before the first form build.
    *
    * @param \Drupal\Core\Form\FormStateInterface $form_state
diff --git a/core/lib/Drupal/Core/Field/WidgetBase.php b/core/lib/Drupal/Core/Field/WidgetBase.php
index 73fb556..ef64fea 100644
--- a/core/lib/Drupal/Core/Field/WidgetBase.php
+++ b/core/lib/Drupal/Core/Field/WidgetBase.php
@@ -341,11 +341,7 @@ public function extractFormValues(FieldItemListInterface $items, array $form, Fo
     // Extract the values from $form_state->getValues().
     $path = array_merge($form['#parents'], array($field_name));
     $key_exists = NULL;
-
-    // Make sure that the massageFormValues() call below always receives an
-    // array as the first argument because some widgets might not impose this
-    // structure on its elements (e.g. the 'options_select' widget).
-    $values = (array) NestedArray::getValue($form_state->getValues(), $path, $key_exists);
+    $values = NestedArray::getValue($form_state->getValues(), $path, $key_exists);
 
     if ($key_exists) {
       // Account for drag-and-drop reordering if needed.