Zoho Desk API : Update an articles returns Unsupported Media Type error

Zoho Desk API : Update an articles returns Unsupported Media Type error

Hi,

Our domain name recently changed and unfortunately we cannot create a 301 redirect to our new domain. 
This results in us having to update our domain name references in our ~500 Zoho Desk articles and ticket answers. 

Since doing a bulk search and replace is not an option in Zoho Desk and updating 500 articles by hand would be very tedious, I'm trying to use the Zoho Desk API to: 

1. Retreive the articles (done!)
2. Update the articles (done!)
3. Update the articles using the 'Update an article' function of the Zoho Desk API.

My problem is with #3, using the Zoho Desk API to update the article. (https://desk.zoho.com/DeskAPIDocument#Articles#Articles_Updateanarticle)

I wrote the following code: 

// Consts
orgId = "20065186XXX";
articleId = "17121000023114XXX"; // ArticleId for testing purposes

// Headers
headerMap = Map();
headerMap.put("Content-Type","application/json");

// Parameters
paramMap = Map();
paramMap.put("title","Hello");
paramMap.put("answer","World");
info paramMap;

// Request URL
requestUrl = "https://desk.zoho.eu/api/v1/articles/" + articleId + "?orgId=" + orgId;

// Update Article
updateArticle = invokeurl
[
url :requestUrl
type :PATCH
headers :headerMap
parameters :paramMap 
connection :"deskarticles"
];

return updateArticle;

To me, it would seem that this code should work. However, when I try to run this I'm receiving the following error: 

{"errorCode":"UNSUPPORTED_MEDIA_TYPE","message":"The given content type is not supported. Please provide the input Content-Type as application/json"}

Some help in how to fix this would be very much appreciated.