diff --git c/core/modules/book/book.module w/core/modules/book/book.module
index 6ddf26c..9cfb7b1 100644
--- c/core/modules/book/book.module
+++ w/core/modules/book/book.module
@@ -334,7 +334,6 @@ function book_pick_book_nojs_submit($form, &$form_state) {
 }
 
 /**
-=======
  * Renders a new parent page select element when the book selection changes.
  *
  * This function is called via Ajax when the selected book is changed on a node