Easeljs is not firing stagemousemove events - easeljs

Question

Using EaselJs 0.6.0, I am trying to drag my stage around using stagemousedown and stagemousemove events. However, while the mouse down event is being caught correctly, the stage mouse move event does not seem to be fired.
var stage = new createjs.Stage("canvas");
createjs.Ticker.addEventListener("tick", tick);
stage.addEventListener("stagemousedown", startDrag);
// Container to drag around
var dragContainer = new createjs.Container();
stage.addChild(dragContainer);
//..... add stuff onto the stage
// Drag
var offset = new createjs.Point();
function startDrag(event) {
console.log('startDrag');
offset.x = stage.mouseX - dragContainer.x;
offset.y = stage.mouseY - dragContainer.y;
event.addEventListener("stagemousemove", doDrag);
}
function doDrag(event) {
console.log('doDrag');
dragContainer.x = event.stageX - offset.x;
dragContainer.y = event.stageY - offset.y;
}
// Update the stage
function tick(event) {
stage.update();
}
Here's a Fiddle
DoDrag is not called. What am I doing wrong?