diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 7ea8087613e..46f65283a3e 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -3105,12 +3105,16 @@ function get_default_npr($thirdparty_seller, $thirdparty_buyer, $idprod=0, $idpr
 
 	if ($idprodfournprice > 0)
 	{
+		if (! class_exists('ProductFournisseur'))
+			require DOL_DOCUMENT_ROOT . '/fourn/class/fournisseur.product.class.php';
 		$prodprice = new ProductFournisseur($db);
 		$prodprice->fetch_product_fournisseur_price($idprodfournprice);
 		return $prodprice->fourn_tva_npr;
 	}
 	elseif ($idprod > 0)
 	{
+		if (! class_exists('Product'))
+			require DOL_DOCUMENT_ROOT . '/product/class/product.class.php';
 		$prod = new Product($db);
 		$prod->fetch($idprod);
 		return $prod->tva_npr;