How to perspective transform a layer and its mask?

[daiappy]

   I have an image in Gimp, that has a layer mask made from a selection I made that is also stored as a channel. I want to use a transform action, (perspective transform),  on that image and to also apply it to the layer mask. When I do this it doesn't transform the layer mask. So, how do I do perspective transform on the image and its mask, (or selection) at the same time?