Animate Createjs container children order (z-index) not working

In Animate 19.2.1 I've been having issues bringing a child MovieClip to the front of its siblings. I'm using MovieClips published from a CreateJS HTML5 canvas document. According to the CreateJS documentation, the following should work:

// Where there are 3 children in the parent...
var child = parent.children[0];
parent.setChildIndex(child, parent.numChildren - 1);

I've also tried:

parent.addChild(child);

The order of children changes, but the child isn't rendered in front of the other children. Any idea where I'm going wrong, and is there a solution to this?

Thanks,

Tim