I am trying to transform a salesorder into an invoice and when I set the amount, it is not working. The amount is getting set as 0, even thought the amount on the salesorder is not 0

fromrecord = 'salesorder';
	 	fromid = salesorderinteralID; //from the search
	 	torecord = 'invoice';
	 	 invoice = nlapiTransformRecord(fromrecord, fromid, torecord);
	 	amount = invoice.getLineItemValue('item','amount',lineitemid);