diff --git a/htdocs/compta/facture/class/api_invoices.class.php b/htdocs/compta/facture/class/api_invoices.class.php
index 09a382a8520..94de562a3c2 100644
--- a/htdocs/compta/facture/class/api_invoices.class.php
+++ b/htdocs/compta/facture/class/api_invoices.class.php
@@ -1580,7 +1580,7 @@ class Invoices extends DolibarrApi
 			}
 
 			if ($this->invoice->type == Facture::TYPE_CREDIT_NOTE) {
-				$amount = -$amount;
+				$amount = price2num(-1 * $amount, 'MT');
 			}
 
 			if ($is_multicurrency) {
diff --git a/htdocs/compta/tva/card.php b/htdocs/compta/tva/card.php
index a7b1e10312a..0b89a923153 100644
--- a/htdocs/compta/tva/card.php
+++ b/htdocs/compta/tva/card.php
@@ -181,7 +181,7 @@ if (empty($reshook)) {
 
 		$amount = price2num(GETPOST("amount", 'alpha'));
 		if ($refund == 1) {
-			$amount = -$amount;
+			$amount = price2num(-1 * $amount);
 		}
 		$object->amount = $amount;
 		$object->label = GETPOST("label", 'alpha');