diff --git a/core/modules/book/src/Form/BookAdminEditForm.php b/core/modules/book/src/Form/BookAdminEditForm.php
index fb1e3e8..85b2fb8 100644
--- a/core/modules/book/src/Form/BookAdminEditForm.php
+++ b/core/modules/book/src/Form/BookAdminEditForm.php
@@ -71,7 +71,7 @@ public function getFormId() {
    */
   public function buildForm(array $form, FormStateInterface $form_state, NodeInterface $node = NULL) {
     $form['#title'] = $node->label();
-    $form['#node'] = $node;
+    $form_state->set('entity', $node);
     $this->bookAdminTable($node, $form);
     $form['save'] = array(
       '#type' => 'submit',
@@ -126,7 +126,7 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
       }
     }
 
-    drupal_set_message($this->t('Updated book %title.', array('%title' => $form['#node']->label())));
+    drupal_set_message($this->t('Updated book %title.', array('%title' => $form_state->get('entity')->label())));
   }
 
   /**