diff --git a/core/modules/book/lib/Drupal/book/BookManager.php b/core/modules/book/lib/Drupal/book/BookManager.php
index 6840a08..5b89ea3 100644
--- a/core/modules/book/lib/Drupal/book/BookManager.php
+++ b/core/modules/book/lib/Drupal/book/BookManager.php
@@ -24,7 +24,7 @@ class BookManager {
    *
    * @var \Drupal\Core\Database\Connection
    */
-  protected $database;
+  protected $connection;
 
   /**
    * Entity manager Service Object.
@@ -50,8 +50,8 @@ class BookManager {
   /**
    * Constructs a BookManager object.
    */
-  public function __construct(Connection $database, EntityManager $entityManager, TranslationInterface $translation) {
-    $this->database = $database;
+  public function __construct(Connection $connection, EntityManager $entityManager, TranslationInterface $translation) {
+    $this->connection = $connection;
     $this->entityManager = $entityManager;
     $this->translation =  $translation;
   }
@@ -77,10 +77,10 @@ public function getAllBooks() {
    */
   protected function loadBooks() {
     $this->books = array();
-    $nids = $this->database->query("SELECT DISTINCT(bid) FROM {book}")->fetchCol();
+    $nids = $this->connection->query("SELECT DISTINCT(bid) FROM {book}")->fetchCol();
 
     if ($nids) {
-      $query = $this->database->select('book', 'b', array('fetch' => \PDO::FETCH_ASSOC));
+      $query = $this->connection->select('book', 'b', array('fetch' => \PDO::FETCH_ASSOC));
       $query->join('menu_links', 'ml', 'b.mlid = ml.mlid');
       $query->fields('b');
       $query->fields('ml');
@@ -284,12 +284,12 @@ public function updateOutline(NodeInterface $node) {
     else {
       // Check in case the parent is not is this book; the book takes precedence.
       if (!empty($node->book['plid'])) {
-        $parent = $database->query("SELECT * FROM {book} WHERE mlid = :mlid", array(
+        $parent = $this->connection->query("SELECT * FROM {book} WHERE mlid = :mlid", array(
           ':mlid' => $node->book['plid'],
         ))->fetchAssoc();
       }
       if (empty($node->book['plid']) || !$parent || $parent['bid'] != $node->book['bid']) {
-        $node->book['plid'] = $database->query("SELECT mlid FROM {book} WHERE nid = :nid", array(
+        $node->book['plid'] = $this->connection->query("SELECT mlid FROM {book} WHERE nid = :nid", array(
           ':nid' => $node->book['bid'],
         ))->fetchField();
         $node->book['parent_mismatch'] = TRUE; // Likely when JS is disabled.
@@ -301,7 +301,7 @@ public function updateOutline(NodeInterface $node) {
     if ($node->book->save()) {
       if ($new) {
         // Insert new.
-        $database->insert('book')
+        $this->connection->insert('book')
           ->fields(array(
             'nid' => $node->id(),
             'mlid' => $node->book['mlid'],
@@ -312,7 +312,7 @@ public function updateOutline(NodeInterface $node) {
         drupal_static_reset('book_get_books');
       }
       else {
-        if ($node->book['bid'] != $database->query("SELECT bid FROM {book} WHERE nid = :nid", array(
+        if ($node->book['bid'] != $this->connection->query("SELECT bid FROM {book} WHERE nid = :nid", array(
           ':nid' => $node->id(),
         ))->fetchField()) {
           // Update the bid for this page and all children.
@@ -372,7 +372,7 @@ public function createMenuName($id) {
    *   A fully loaded menu link that is part of the book hierarchy.
    */
   function updateID($book_link) {
-    $query = $database->select('menu_links');
+    $query = $this->connection->select('menu_links');
     $query->addField('menu_links', 'mlid');
     for ($i = 1; $i <= MENU_MAX_DEPTH && $book_link["p$i"]; $i++) {
       $query->condition("p$i", $book_link["p$i"]);
@@ -380,7 +380,7 @@ function updateID($book_link) {
     $mlids = $query->execute()->fetchCol();
 
     if ($mlids) {
-      $database->update('book')
+      $this->connection->update('book')
         ->fields(array('bid' => $book_link['bid']))
         ->condition('mlid', $mlids, 'IN')
         ->execute();