I get a ReferenceError in the following userscript code:

```
// ==UserScript==
// @name          ...
// @namespace     ...
// @description   ...
// @include       ...
// @grant         GM_xmlhttpRequest
// ==/UserScript==

console.log(GM_info);
try
{
    console.log(GM_xmlhttpRequest({ method: "GET", url: "http://google.ca/", synchronous: true }).readyState);
}
catch (e)
{
    console.log(e);
}
...

```

It first logs `GM_info` successfully, then logs the ReferenceError. (I'm using Firefox/Firebug.)

> 
> ReferenceError: GM\_xmlhttpRequest is not defined
> 
> 
> 

Why do I get this error?