diff --git a/MysqliDb.php b/MysqliDb.php
index cea80ae..3b585e3 100644
--- a/MysqliDb.php
+++ b/MysqliDb.php
@@ -1427,7 +1427,7 @@ public function getInsertId()
      */
     public function escape($str)
     {
-        return $this->mysqli()->real_escape_string($str);
+        return $str ? $this->mysqli()->real_escape_string($str) : $str;
     }
 
     /**