diff --git a/classes/db/DB.class.php b/classes/db/DB.class.php
index 2d1f9dd27..f49e8710b 100644
--- a/classes/db/DB.class.php
+++ b/classes/db/DB.class.php
@@ -315,6 +315,7 @@
             if($source_args) $args = @clone($source_args);
 
             require_once(_XE_PATH_.'classes/xml/xmlquery/DBParser.class.php');
+            require_once(_XE_PATH_.'classes/xml/xmlquery/argument/Argument.class.php');
             require_once(_XE_PATH_.'classes/db/queryparts/expression/Expression.class.php');
             require_once(_XE_PATH_.'classes/db/queryparts/expression/SelectExpression.class.php');
             require_once(_XE_PATH_.'classes/db/queryparts/expression/InsertExpression.class.php');