diff --git a/serial.inc b/serial.inc
index 28e12a3..d341036 100644
--- a/serial.inc
+++ b/serial.inc
@@ -154,9 +154,9 @@ function _serial_generate_value($bundle, $field_name, $delete = TRUE) {
   $sid = isset($sid) ? $sid : 0;
 
   // Delete the temporary record.
-  if ($delete && ($sid % 10) == 0) {
+  if ($delete && $sid && ($sid % 10) == 0) {
     db_delete($table)
-      ->condition('uniqid', $uniqid)
+      ->condition('sid', $sid, '<')
       ->execute();
   }