diff --git a/core/themes/bartik/css/components/book.css b/core/themes/bartik/css/components/book.css
index 9f166b97397..82e22eee889 100644
--- a/core/themes/bartik/css/components/book.css
+++ b/core/themes/bartik/css/components/book.css
@@ -1,3 +1,8 @@
+/**
+ * @file
+ * Bartik specific styling for the Book module.
+ */
+
 .book-navigation .menu {
   border-top: 1px solid #d6d6d6;
 }