diff --git a/addons/website_sale/static/src/js/website_sale.js b/addons/website_sale/static/src/js/website_sale.js
index a48483b5349..cc6a57e2796 100644
--- a/addons/website_sale/static/src/js/website_sale.js
+++ b/addons/website_sale/static/src/js/website_sale.js
@@ -143,7 +143,7 @@ $('.oe_website_sale').each(function () {
         if ($input.data('update_change')) {
             return;
         }
-      var value = parseInt($input.val(), 10);
+      var value = parseInt($input.val() || 0, 10);
       var $dom = $(this).closest('tr');
       var default_price = parseFloat($dom.find('.text-danger > span.oe_currency_value').text());
       var $dom_optional = $dom.nextUntil(':not(.optional_product.info)');
@@ -164,7 +164,7 @@ $('.oe_website_sale').each(function () {
         'set_qty': value})
         .then(function (data) {
             $input.data('update_change', false);
-            if (value !== parseInt($input.val(), 10)) {
+            if (value !== parseInt($input.val() || 0, 10)) {
                 $input.trigger('change');
                 return;
             }
@@ -211,7 +211,7 @@ $('.oe_website_sale').each(function () {
         var product_id = +$input.closest('*:has(input[name="product_id"])').find('input[name="product_id"]').val();
         var min = parseFloat($input.data("min") || 0);
         var max = parseFloat($input.data("max") || Infinity);
-        var quantity = ($link.has(".fa-minus").length ? -1 : 1) + parseFloat($input.val(),10);
+        var quantity = ($link.has(".fa-minus").length ? -1 : 1) + parseFloat($input.val() || 0, 10);
         // if they are more of one input for this product (eg: option modal)
         $('input[name="'+$input.attr("name")+'"]').add($input).filter(function () {
             var $prod = $(this).closest('*:has(input[name="product_id"])');