diff --git a/classes/xml/XmlQueryParser.class.php b/classes/xml/XmlQueryParser.class.php
index 812c0097b..26ee32497 100644
--- a/classes/xml/XmlQueryParser.class.php
+++ b/classes/xml/XmlQueryParser.class.php
@@ -469,7 +469,7 @@
         */
         function getDefault($name, $value) {
             $db_info = Context::getDBInfo ();
-            if(!$value) return;
+            if(!isset($value)) return;
             $str_pos = strpos($value, '(');
             if($str_pos===false) return '"'.$value.'"';