Error on creating quote detail with javascript "The unit id is missing"

var entity = {};
            entity.Quantity = quantity;
            entity.PricePerUnit = { Value: parseFloat(price).toFixed(2) };
            entity.QuoteId = {
                Id: quoteGuid,
                LogicalName: "quote"
            };
            entity.ProductId = {
                Id: "4d27a5a5-bf45-e311-b5c4-d48564519c0d",
                LogicalName: "product"
            };
            entity.UoMId = {
                Id: "101F9956-A121-4047-8844-9B02B438272B",
                LogicalName: "uom"
            };

            entity.IsProductOverridden = true;
            var url = window.location.protocol + "//" + window.location.hostname;
            var req = new XMLHttpRequest();
            req.open("POST", encodeURI(url + "/XRMServices/2011/OrganizationData.svc/QuoteDetailSet"), true);
            req.setRequestHeader("Accept", "application/json");
            req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
            req.onreadystatechange = function () {
                if (this.readyState === 4) {
                    req.onreadystatechange = null;
                    if (this.status === 201) {
                        var result = JSON.parse(req.responseText).d;
                        var newEntityId = result.QuoteDetailId;
                        alert("success");
                        getAllProductsOnQuote();
                    }
                    else {
                        alert(this.statusText);
                    }
                }
            };
            req.send(JSON.stringify(entity));