diff --git a/core/modules/book/src/BookManager.php b/core/modules/book/src/BookManager.php
index 17bc0d9..eb5b582 100644
--- a/core/modules/book/src/BookManager.php
+++ b/core/modules/book/src/BookManager.php
@@ -252,7 +252,7 @@ public function updateOutline(NodeInterface $node) {
     // Prevent changes to the book outline if the node being saved is not the
     // default revision.
     if (!$node->isDefaultRevision()) {
-      drupal_set_message($this->t('The book outline could not be changed because a non-default revision (for example: a new draft revision) of the content has been created.'), 'error');
+      drupal_set_message($this->t('You can only change the book outline for the published version of this content.'), 'error');
       return FALSE;
     }
 
diff --git a/core/modules/book/tests/src/Functional/BookContentModerationTest.php b/core/modules/book/tests/src/Functional/BookContentModerationTest.php
index 5b5fe34..0b9c831 100644
--- a/core/modules/book/tests/src/Functional/BookContentModerationTest.php
+++ b/core/modules/book/tests/src/Functional/BookContentModerationTest.php
@@ -60,7 +60,7 @@ public function testBookWithForwardRevisions() {
     $edit['book[pid]'] = $book_1_nodes[3]->id();
     $this->drupalPostForm('node/' . $book_1_nodes[1]->id() . '/edit', $edit, t('Save and Create New Draft'));
 
-    $this->assertSession()->pageTextContains('The book outline could not be changed because a non-default revision (for example: a new draft revision) of the content has been created.');
+    $this->assertSession()->pageTextContains('You can only change the book outline for the published version of this content.');
 
     // Check that the book outline did not change.
     $this->book = $book_1;
@@ -71,7 +71,7 @@ public function testBookWithForwardRevisions() {
     $edit['book[bid]'] = $book_2->id();
     $this->drupalPostForm('node/' . $book_1_nodes[1]->id() . '/edit', $edit, t('Save and Create New Draft'));
 
-    $this->assertSession()->pageTextContains('The book outline could not be changed because a non-default revision (for example: a new draft revision) of the content has been created.');
+    $this->assertSession()->pageTextContains('You can only change the book outline for the published version of this content.');
 
     // Check that the book outline did not change.
     $this->book = $book_1;
diff --git a/core/modules/book/tests/src/Functional/BookTest.php b/core/modules/book/tests/src/Functional/BookTest.php
index df19242..640859f 100644
--- a/core/modules/book/tests/src/Functional/BookTest.php
+++ b/core/modules/book/tests/src/Functional/BookTest.php
@@ -23,20 +23,6 @@ class BookTest extends BrowserTestBase {
   public static $modules = ['book', 'block', 'node_access_test', 'book_test'];
 
   /**
-   * A book node.
-   *
-   * @var \Drupal\node\NodeInterface
-   */
-  protected $book;
-
-  /**
-   * A user with permission to create and edit books.
-   *
-   * @var object
-   */
-  protected $bookAuthor;
-
-  /**
    * A user with permission to view a book and access printer-friendly version.
    *
    * @var object