diff --git a/book.module b/book.module
--- a/book.module	Mon Jun 06 09:55:00 2011
+++ b/book.module	Wed Jun 22 09:21:07 2011
@@ -389,6 +389,11 @@
  */
 function book_form_node_form_alter(&$form, &$form_state, $form_id) {
   $node = $form['#node'];
+  // check to see if this content type is allowed in a book outline.
+  if (!in_array($node->type, variable_get('book_allowed_types',FALSE))) {
+    // if not, just escape.
+    return;
+  }
   $access = user_access('administer book outlines');
   if (!$access) {
     if (user_access('add content to books') && ((!empty($node->book['mlid']) && !empty($node->nid)) || book_type_is_allowed($node->type))) {