Index: modules/book/book.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/book/book.module,v
retrieving revision 1.488
diff -u -p -r1.488 book.module
--- modules/book/book.module	30 Mar 2009 05:40:44 -0000	1.488
+++ modules/book/book.module	9 Apr 2009 12:10:54 -0000
@@ -913,10 +913,12 @@ function template_preprocess_book_naviga
     }
 
     if ($book_link['plid'] && $parent = book_link_load($book_link['plid'])) {
-      $parent_href = url($parent['href']);
-      drupal_add_link(array('rel' => 'up', 'href' => $parent_href));
-      $variables['parent_url'] = $parent_href;
-      $variables['parent_title'] = check_plain($parent['title']);
+      if ($parent['access']) {
+        $parent_href = url($parent['href']);
+        drupal_add_link(array('rel' => 'up', 'href' => $parent_href));
+        $variables['parent_url'] = $parent_href;
+        $variables['parent_title'] = check_plain($parent['title']);
+      }
     }
 
     if ($next = book_next($book_link)) {