diff --git a/core/modules/book/src/BookManager.php b/core/modules/book/src/BookManager.php
index 3e14c40..4538658 100644
--- a/core/modules/book/src/BookManager.php
+++ b/core/modules/book/src/BookManager.php
@@ -249,6 +249,12 @@ public function updateOutline(NodeInterface $node) {
       return FALSE;
     }
 
+    // Prevent changes to the book outline if the node being saved is not the
+    // default revision.
+    if (!$node->isDefaultRevision()) {
+      return FALSE;
+    }
+
     if (!empty($node->book['bid'])) {
       if ($node->book['bid'] == 'new') {
         // New nodes that are their own book.
diff --git a/core/modules/book/tests/src/Functional/BookTest.php b/core/modules/book/tests/src/Functional/BookTest.php
index 66edec9..d81b370 100644
--- a/core/modules/book/tests/src/Functional/BookTest.php
+++ b/core/modules/book/tests/src/Functional/BookTest.php
@@ -749,4 +749,21 @@ public function testBookNavigationBlockOnUnpublishedBook() {
     $this->assertText($this->book->label(), 'Unpublished book with "Show block only on book pages" book navigation settings.');
   }
 
+  /**
+   * Tests that forward revisions can not modify the book outline.
+   */
+  public function testBookWithForwardRevisions() {
+    $this->drupalLogin($this->bookAuthor);
+    $this->book = $this->createBookNode('new');
+
+    /** @var \Drupal\book\BookManagerInterface $book_manager */
+    $book_manager = $this->container->get('book.manager');
+
+    $this->book->setNewRevision(TRUE);
+    $this->book->isDefaultRevision(FALSE);
+
+    $return = $book_manager->updateOutline($this->book);
+    $this->assertFalse($return, 'A forward revision can not change the book outline.');
+  }
+
 }