diff --git a/htdocs/compta/facture/class/api_invoices.class.php b/htdocs/compta/facture/class/api_invoices.class.php
index 643fb7eddd0..3c9f0af29bc 100644
--- a/htdocs/compta/facture/class/api_invoices.class.php
+++ b/htdocs/compta/facture/class/api_invoices.class.php
@@ -996,6 +996,8 @@ class Invoices extends DolibarrApi
      */
     public function markAsCreditAvailable($id)
     {
+		require_once DOL_DOCUMENT_ROOT.'/core/class/discount.class.php';
+		
         if (!DolibarrApiAccess::$user->rights->facture->creer) {
             throw new RestException(401);
         }