colorTransform erases dropShadow filter

[ziriguidum]

I'm using this code into a mouse over and mouse out listener , to change the color of a TextField.

var ct:Color = new Color();
ct.setTint(0xFF0000, 0.5);
mc.transform.colorTransform = ct;

The problem is that the dropShadow filter associated with the TextField (applied in the flash UI) is gone when this colorTransform applies.

Do anybody knows why?
Should I apply the filter dynamically, is that the only solution ??

Thnks!