diff --git a/htdocs/compta/facture/apercu.php b/htdocs/compta/facture/apercu.php
index f12b4235fbd..3a726067290 100644
--- a/htdocs/compta/facture/apercu.php
+++ b/htdocs/compta/facture/apercu.php
@@ -30,6 +30,7 @@
 
 require("./pre.inc.php");
 require_once(DOL_DOCUMENT_ROOT."/facture.class.php");
+require_once(DOL_DOCUMENT_ROOT.'/lib/invoice.lib.php');
 if ($conf->projet->enabled) require_once(DOL_DOCUMENT_ROOT."/project.class.php");