[Moo] element.get tween error?

[Dailce]

I have this code that works in 1.2

this.fx[0].element.get("tween", {
                property: "height",
                duration: 300,
                wait: false
 }).start(c + "px")

But I can't seem to get it to work in mootools 1.3'
What's changed?

I'm getting a firebug error:  "this.fx[0].element.get("tween",
{property: "height", duration: 300, wait: false}).start is not a
function"