Sdk / request always responds with `constructor {}`

I am developing a Firefox Add-on (SDK) and communicating with the Request module. I copied and applied the Twitter-API example from the Mozilla doc to minelib/main.js

var Request = require("sdk/request").Request;
var latestTweetRequest = Request({
  url:   "https://api.twitter.com/1/statuses/user_timeline.json?screen_name=mozhacks&count=1",
  onComplete: function (response) {
    var tweet = response.json[0];
    console.log("User: " + tweet.user.screen_name);
    console.log("Tweet: " + tweet.text);
  }
});

Request({
  url: "http://api.twitter.com/1/account/rate_limit_status.json",
  onComplete: function (response) {
    console.log(response); // <--- constructor {}
    if (response.json.remaining_hits) {
      latestTweetRequest.get();
    } else {
      console.log("You have been rate limited!");
    }
  }
}).get();

      

        
        
        
      

    

and run the extension with cfx run

. Then each answer is just

constructor {}

      

        
        
        
      

    

and no error occurs.

I installed REST API on localhost and found that no requests were being made.

What could be causing this?