diff --git a/htdocs/comm/propal/card.php b/htdocs/comm/propal/card.php
index cb2001fc399..d3c435bf195 100644
--- a/htdocs/comm/propal/card.php
+++ b/htdocs/comm/propal/card.php
@@ -1963,7 +1963,7 @@ if ($action == 'create') {
 
 			$thirdparty = $soc;
 			$discount_type = 0;
-			$backtopage = $_SERVER["PHP_SELF"].'?socid='.$thirdparty->id.'&action='.$action.'&origin='.urlencode(GETPOST('origin')).'&originid='.urlencode(GETPOSTINT('originid'));
+			$backtopage = $_SERVER["PHP_SELF"].'?socid='.$thirdparty->id.'&action='.$action.'&origin='.urlencode((string) (GETPOST('origin'))).'&originid='.urlencode((string) (GETPOSTINT('originid')));
 			include DOL_DOCUMENT_ROOT.'/core/tpl/object_discounts.tpl.php';
 			print '</td></tr>';
 		}