diff --git a/htdocs/webservices/server_invoice.php b/htdocs/webservices/server_invoice.php
index 54f5e3c564c..9318328a060 100644
--- a/htdocs/webservices/server_invoice.php
+++ b/htdocs/webservices/server_invoice.php
@@ -30,6 +30,7 @@ require_once DOL_DOCUMENT_ROOT.'/core/lib/ws.lib.php';
 require_once DOL_DOCUMENT_ROOT.'/user/class/user.class.php';
 
 require_once DOL_DOCUMENT_ROOT.'/compta/facture/class/facture.class.php';
+require_once DOL_DOCUMENT_ROOT.'/commande/class/commande.class.php';
 
 
 dol_syslog("Call Dolibarr webservices interfaces");