diff --git a/core/modules/book/src/Plugin/Block/BookNavigationBlock.php b/core/modules/book/src/Plugin/Block/BookNavigationBlock.php
index 1a68622..927cba9 100644
--- a/core/modules/book/src/Plugin/Block/BookNavigationBlock.php
+++ b/core/modules/book/src/Plugin/Block/BookNavigationBlock.php
@@ -182,10 +182,8 @@ public function build() {
    * {@inheritdoc}
    */
   public function getCacheContexts() {
-    // The "Book navigation" block must be cached per role and book navigation
-    // context.
+    // The "Book navigation" block varies by the book navigation cache context.
     return [
-      'user.roles',
       'route.book_navigation',
     ];
   }