--- /usr/home/fch/tmp/Product.php	2009-09-30 17:36:08.000000000 +0200
+++ /usr/local/www/prestashop/classes/Product.php	2009-09-30 17:38:08.000000000 +0200
@@ -1277,8 +1277,14 @@
 			$price -= $reduc;
 
 		// Quantity discount
-		if ($quantity > 1 AND ($qtyD = QuantityDiscount::getDiscountFromQuantity($id_product, $quantity)))
-			$price -= QuantityDiscount::getValue($price, $qtyD->id_discount_type, $qtyD->value);
+		if ($quantity > 1 AND ($qtyD = QuantityDiscount::getDiscountFromQuantity($id_product, $quantity))) {
+			$discount = QuantityDiscount::getValue($price, $qtyD->id_discount_type, $qtyD->value);
+
+			if (!QuantityDiscount::isPercent($qtyD->id_discount_type) && $usetax)
+				$discount *= (1 + ($tax / 100));
+
+			$price -= $discount;
+		}
 
 		// Group reduction
 		if ($id_customer)
--- /usr/home/fch/tmp/QuantityDiscount.php	2009-09-30 17:38:53.000000000 +0200
+++ /usr/local/www/prestashop/classes/QuantityDiscount.php	2009-09-30 17:38:59.000000000 +0200
@@ -49,7 +49,7 @@
 
     public static function getValue($product_price, $id_discount_type, $value)
     {
-		if ($id_discount_type == 1)
+		if (self::isPercent($id_discount_type))
 		{
 			$percentage = $value / 100;
 			return $percentage * floatval($product_price);
@@ -59,6 +59,11 @@
 		return 0;
     }
 
+	public static function isPercent($id_discount_type)
+	{
+		return $id_discount_type == 1;
+	}
+
     public static function getQuantityDiscounts($id_product, $price)
 	{
 		global $cookie;