update Cureency Exchange via API - Error

update Cureency Exchange via API - Error

Hey team, I've looked to this wiki: 
https://www.zoho.com/crm/developer/docs/api/v4/update-currencies.html

That's what I need to do, to update 2 currency exchanges from my CRM, so new deals will take the new rate. 

So, I have this code: 
// Create a map that holds the values of the new contact that needs to be created
new_exchange = Map();
new_exchange.put("exchange_rate", "234");
response = invokeUrl
[
type: PUT
parameters: new_exchange
connection: "zohocrmcustomconnect"
];
info response;



But the response I get is:
{"code":"INVALID_DATA","details":{"expected_data_type":"jsonobject"},"message":"body","status":"error"}


I've tried to chat with zoho CRM support but they told me that I should change my home currency, which is not possible. 
Any Idea?