diff --git a/menu_block.module b/menu_block.module
index 7010188..96ba569 100644
--- a/drupal/sites/all/modules/menu_block/menu_block.module
+++ b/drupal/sites/all/modules/menu_block/menu_block.module
@@ -372,7 +372,12 @@ function menu_tree_block_data(array &$config) {
   if ($config['level'] > 1 || $config['parent_mlid']) {
     if ($config['parent_mlid']) {
       $parent_item = menu_link_load($config['parent_mlid']);
-      menu_tree_prune_tree($tree, $config['level'], $parent_item);
+      if (!empty($parent_item)) {
+        menu_tree_prune_tree($tree, $config['level'], $parent_item);
+      }
+      else {
+        menu_tree_prune_tree($tree, $config['level']);
+      }
     }
     else {
       menu_tree_prune_tree($tree, $config['level']);