Applying Coupon Code via Suitescript

I am trying to create a sales order and apply a coupon code to the order via suitescript however I always receive "invalid couponcode reference key 123"

If I exclude the coupon code and go into the sales order I have created I can apply the code 123 without issue.

Am I missing something obvious here?

Code I am using is:

// Create a new sales order and set the customer  var record = nlapiCreateRecord('salesorder');  record.setFieldValue('entity', 1645);    record.selectNewLineItem('item');  record.setCurrentLineItemValue('item', 'item', 1008 );  record.setCurrentLineItemValue('item', 'quantity', '1');  record.setCurrentLineItemValue('item', 'custcol9', '1123123');  record.commitLineItem('item');    record.setFieldValue('couponcode', 123);    var id = nlapiSubmitRecord(record, true);