Affine transform on transparent image introduce black

The input image has transparent pixels. After the transform, the transparent 
pixels are partially black. Here's the command I used:

gm convert  -affine 1,0,0.785,1,0,0 -transform before.miff after2.miff

The input and output images are at http://home.roadrunner.com/foxhunter. I'm 
using GraphicsMagick 1.2. Please let me know if you need any more 
information.

-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference 
Don't miss this year's exciting event. There's still time to save $100. 
Use priority code J8TL2D2. 
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone