diff --git a/term_reference_tree.module b/term_reference_tree.module
index 91313ef..5421a1c 100644
--- a/term_reference_tree.module
+++ b/term_reference_tree.module
@@ -138,12 +138,14 @@ function _term_reference_tree_get_children($tid, $vid) {
   // module is enabled).
   $select = db_select('taxonomy_term_data', 'd');
   $select->join('taxonomy_term_hierarchy', 'h', 'd.tid = h.tid');
+  $select->join('taxonomy_vocabulary', 'v', 'v.vid = d.vid');
+  $select->addField('v', 'machine_name', 'vocabulary_machine_name');
   $result = $select->fields('d', array('tid', 'name'))
     ->condition('d.vid', $vid, '=')
     ->condition('h.parent', $tid, '=')
-    ->orderBy('weight')
-    ->orderBy('name')
-    ->orderBy('tid')
+    ->orderBy('d.weight')
+    ->orderBy('d.name')
+    ->orderBy('d.tid')
     ->execute();
 
   $terms = array();
diff --git a/term_reference_tree.widget.inc b/term_reference_tree.widget.inc
index 8bae7a1..66a6b39 100644
--- a/term_reference_tree.widget.inc
+++ b/term_reference_tree.widget.inc
@@ -278,13 +278,15 @@ function term_reference_tree_process_checkbox_tree($element, $form_state) {
 
     if (empty($element['#options'])) {
       $element['#options_tree'] = _term_reference_tree_get_term_hierarchy($element['#parent_tid'], $element['#vocabulary'], $allowed, $element['#filter_view'], '', $value);
+      $vocabulary = taxonomy_vocabulary_load($element['#vocabulary']);
       
       $required = $element['#required'];
       if ($element['#max_choices'] == 1 && !$required) {
         array_unshift($element['#options_tree'], (object) array(
           'tid' => '',
           'name' => 'N/A',
-          'depth' => 0
+          'depth' => 0,
+          'vocabulary_machine_name' => $vocabulary->machine_name,
           )
         );
       }
@@ -661,7 +663,7 @@ function _term_reference_tree_build_item(&$element, &$term, &$form_state, &$valu
   }
 
   $t = null;
-  if(module_exists('locale')) {
+  if(module_exists('locale') && $term->tid) {
     $t = taxonomy_term_load($term->tid);
     $term_name = entity_label('taxonomy_term', $t);
   } else {