Uncrop doesn't work when there is an alpha channel

[ofnuts]

The un-crop just adds a transparent area around the layer:

Looking at the alpha channel (here, by adding a layer mask) show that the problem is that the alpha of the extended layer has been filled with 0's:

Setting alpha to 100% on these pixels makes the un-cropping appear:

[bootchk]

Thanks for reporting. I will look at it.

Off the top of my head, there is recent, related issue #104. Which I fixed. Maybe I broke something, or maybe your issue is fixed already, or maybe another fix is needed.