diff --git notifications.install notifications.install
index ed8d87a..6871c03 100644
--- notifications.install
+++ notifications.install
@@ -373,4 +373,13 @@ function notifications_update_6003() {
 function notifications_update_6004() {
   drupal_get_schema(NULL, TRUE);
   return array();
-}
\ No newline at end of file
+}
+
+/**
+ * Add an index to {notifications} for notifications_queue().
+ */
+function notifications_update_6005() {
+  $ret = array();
+  db_add_index($ret, 'notifications', 'queue', array(status, event_type, send_interval, uid));
+  return $ret;
+}