diff --git a/core/modules/field/modules/entityreference/entityreference.module b/core/modules/field/modules/entityreference/entityreference.module
index 4d17efa..d0ad084 100644
--- a/core/modules/field/modules/entityreference/entityreference.module
+++ b/core/modules/field/modules/entityreference/entityreference.module
@@ -288,12 +288,9 @@ function entityreference_field_widget_info_alter(array &$info) {
  */
 function entityreference_options_list($field, $instance = NULL, $entity_type = NULL, $entity = NULL) {
   $options = entityreference_get_selection_handler($field, $instance, $entity_type, $entity)->getReferencableEntities();
-  if (count($options) == 1) {
-    // Change the optgroup to a flat array.
-    $key = key($options);
-    $options = $options[$key];
-  }
-  return $options;
+  // Change the optgroup to a flat array if the results are from a single
+  // bundle.
+  return (count($options) == 1) ? reset($options) : $options;
 }
 
 /**