Play MovieClip within MovieClip

Hello,
I have a Box which have converted to a movieclip, and called it “box_mc1”.

Within “box_mc1” I have a circle which is another movieclip by the name of “circle_mc1”.

circle_mc1 consist of 10 frames, the first has a “stop()” action on it.

box_mc1 has the following code:

on (release) {
_root.box_mc1.circle_mc1.play();
}

This does not work.

Anyone know what I’m doing wrong?