diff --git a/core/modules/book/templates/book-tree.html.twig b/core/modules/book/templates/book-tree.html.twig
index d9c31db..5ac0c0b 100644
--- a/core/modules/book/templates/book-tree.html.twig
+++ b/core/modules/book/templates/book-tree.html.twig
@@ -10,7 +10,7 @@
  *   - attributes: HTML attributes for the book item.
  *   - below: The book item child items.
  *   - title: The book link title.
- *   - url: The book link url, instance of \Drupal\Core\Url
+ *   - url: The book link URL, instance of \Drupal\Core\Url.
  *
  * @ingroup themeable
  */
diff --git a/core/themes/classy/templates/navigation/book-tree.html.twig b/core/themes/classy/templates/navigation/book-tree.html.twig
index c819bbc..f39d8bf 100644
--- a/core/themes/classy/templates/navigation/book-tree.html.twig
+++ b/core/themes/classy/templates/navigation/book-tree.html.twig
@@ -1,7 +1,7 @@
 {#
 /**
  * @file
- * Default theme implementation to display a book tree.
+ * Theme override to display a book tree.
  *
  * Returns HTML for a wrapper for a book sub-tree.
  *
@@ -10,9 +10,7 @@
  *   - attributes: HTML attributes for the book item.
  *   - below: The book item child items.
  *   - title: The book link title.
- *   - url: The book link url, instance of \Drupal\Core\Url
- *
- * @ingroup themeable
+ *   - url: The book link URL, instance of \Drupal\Core\Url.
  */
 #}
 {% import _self as book_tree %}