TIFF with unspecified alpha-channels loads as invalid ARGB32PM

I have some TIFF images that I'm including in my project as resources and load in to my widget as pixmaps. These TIFF images include an alpha channel which I use to make portions of each image transparent. I then render a video player widget that mimics Apple's old Quicktime 7 player interface. On versions of Qt prior to 5.5.1, the images rendered perfectly. Can't tell the difference between my widget and Apple's quicktime player, but on 5.5.1, I see spurious black pixels rendered in areas where the pixmaps should be transparent.