diff --git a/modules/callbacks.inc b/modules/callbacks.inc
index e7c283a..467c684 100644
--- a/modules/callbacks.inc
+++ b/modules/callbacks.inc
@@ -781,7 +781,7 @@ function entity_metadata_comment_properties_access($op, $property, $entity = NUL
 /**
  * Access callback for the taxonomy entities.
  */
-function entity_metadata_taxonomy_access($op, $entity = NULL, $account = NULL, $entity_type) {
+function entity_metadata_taxonomy_access($op, $entity = NULL, $account = NULL, $entity_type = NULL) {
   if ($entity_type == 'taxonomy_vocabulary') {
     return user_access('administer taxonomy', $account);
   }