diff --git a/htdocs/commande/card.php b/htdocs/commande/card.php
index 0fe49cf9f12..c10591b4e45 100644
--- a/htdocs/commande/card.php
+++ b/htdocs/commande/card.php
@@ -679,7 +679,7 @@ if (empty($reshook))
 			setEventMessages($langs->trans('ErrorFieldRequired', $langs->transnoentitiesnoconv('Type')), null, 'errors');
 			$error++;
 		}
-		if ($prod_entry_mode == 'free' && empty($idprod) && (! ($price_ht >= 0) || $price_ht == '') && (! ($price_ht_devise >= 0) || $price_ht_devise == '')) 	// Unit price can be 0 but not ''
+		if ($prod_entry_mode == 'free' && empty($idprod) && $price_ht == '' && $price_ht_devise == '') 	// Unit price can be 0 but not ''. Also price can be negative for order.
 		{
 			setEventMessages($langs->trans("ErrorFieldRequired", $langs->transnoentitiesnoconv("UnitPriceHT")), null, 'errors');
 			$error++;