I try to implement a simple XHR upload to Node.js (via [Formidable](https://github.com/felixge/node-formidable)). The problem is that if I set 

```
xhr.setRequestHeader("Content-Type", "multipart/form-data");

```

node gives me error:

```
Error: bad content-type header, no multipart boundary

```

If I set boundary to just a random string nothing happens. The browser just hangs on POST and waits for server response.

The point is that if I use formidable with regular synchronous POST everything works fine. 

Anyone tried to use [Formidable](https://github.com/felixge/node-formidable) with XHR upload?