diff --git a/taxonomy_entity_index.module b/taxonomy_entity_index.module
index 97798e2..1319a7e 100644
--- a/taxonomy_entity_index.module
+++ b/taxonomy_entity_index.module
@@ -414,6 +414,7 @@ function taxonomy_entity_index_field_is_indexable($field) {
  * @see taxonomy_entity_index_get_terms_from_field()
  */
 function taxonomy_entity_index_get_terms_from_taxonomy_term_reference($entity_type, $entity, $field) {
+  $terms = array();
   if ($items = field_get_items($entity_type, $entity, $field['field_name'])) {
     foreach ($items as $delta => $item) {
       $terms[] = array(