Can't access element attributes by array index

I'm having issues iterating over the list of attributes on an element. Here's sample code:

``` js
domino = require('domino');

window = domino.createWindow("<h1 lang='en'>Hello</h1>");
h1 = window.document.body.firstChild;

// Outputs 1
console.log(h1.attributes.length);
// Returns undefined, expected an object
console.log(h1.attributes[0]);
```
