diff --git a/core/attributedef.class.inc.php b/core/attributedef.class.inc.php
index 50c7f9860..3b44fae0a 100644
--- a/core/attributedef.class.inc.php
+++ b/core/attributedef.class.inc.php
@@ -1125,6 +1125,11 @@ class AttributeBoolean extends AttributeInteger
 		if ($value) return 1;
 		return 0;
 	}
+
+	public function GetAsXML($sValue, $oHostObject = null)
+	{
+		return $sValue ? '1' : '0';
+	}
 }
 
 /**