node-oauth not happy.

happy.js

var OAuth= require('oauth').OAuth;
var events = require('events');
var http = require('http');
var eyes = require('eyes');
var _ = require('underscore');

tweet = function() {
  var oAuth= new OAuth("http://twitter.com/oauth/request_token",
    "http://twitter.com/oauth/access_token", 
    "vknnKEthhunReqNATrhjvg",  "", 
    "1.0A", null, "HMAC-SHA1");       
  oAuth.post("http://api.twitter.com/1/statuses/update.json", "411642032-lQnQzVEumOCFXcENCRA1sTcrEjRLPaI0jxEXGW9F", 
    "", {"status":"TEST oAuth twitter from Node"}, function(error, data) {
    if(error) console.log(require('sys').inspect(error))
    else console.log(data)
    });         
};

tweet();

not_happy.js

var OAuth= require('oauth').OAuth;
var events = require('events');
var http = require('http');
var eyes = require('eyes');
var _ = require('underscore');


Object.prototype.tweet = function() {
  var oAuth= new OAuth("http://twitter.com/oauth/request_token",
    "http://twitter.com/oauth/access_token", 
    "vknnKEthhunReqNATrhjvg",  "", 
    "1.0A", null, "HMAC-SHA1");       
  oAuth.post("http://api.twitter.com/1/statuses/update.json", "411642032-lQnQzVEumOCFXcENCRA1sTcrEjRLPaI0jxEXGW9F", 
    "", {"status":"TEST oAuth twitter from Node"}, function(error, data) {
    if(error) console.log(require('sys').inspect(error))
    else console.log(data)
    });         
};


Object.tweet();

Error message:

{ statusCode: 401,
data: '{"error":"Could not authenticate with OAuth.","request":"/1/statuses/update.json"}' }

When sending like that I think the content-type is set to "application/x-www-form-urlencoded" where "application/json" is expected.