Masking ComboBox component

[blu3]

Hi,

I have a problem masking ComboBox component. I am using following code:

import fl.controls.ComboBox;

var cb:ComboBox = new ComboBox();
cb.addItem({data:1, label:"One"});
cb.addItem({data:2, label:"Two"});
cb.addItem({data:3, label:"Three"});
cb.addItem({data:4, label:"Four"});
addChild(cb);

var masker:Sprite = new Sprite();
masker.graphics.beginFill(0xFFFFFF);
masker.graphics.drawRect(0,0,cb.width,cb.height);
masker.graphics.endFill();
addChild(masker);

cb.mask = masker;

And ComboBox is masked fine (as test i used masker which is half height and width of the combobox and then only half of combobox was displayed) until i click on it, then whole ComboBox opens just as if it isn't masked. It looks like it breaks the masking thing :/ Did anyone have similar problems or maybe know what am i doing wrong?

thanks,
best regards