Black background for transparent PNGs

This might have been discussed already, but I didn't see it after searching around.

Running elgg 1.5 with an unmodified SimpleBlueWhite theme.  After adding transparent PNG files to the site (either in the files section or as group icons) the backgrounds are changed to black.

I believe this is do to how Imagemagick handles transparent PNG files, but I have no idea how to fix that one (relatively new to elgg).