display: Cropping box does not draw properly with other windows over it

Ubuntu Raring 64bit, up to date.
Imagemagick 8:6.7.7.10-5ubuntu2

I haven't seen any python/apport updates, so I assume it's still broken (bug 1150335)

Steps to reproduce:
Open a picture with "display"
Place another window over the canvas (even IM's own menu would do)
- You might need to change the focus/raise model of your window manager to achieve that for other windows
Select "Transform->Crop" from IM's menu
Try to select an area around the obstructing window.

Observed: see the attachment

Expected: Whole rectangle being painted.

I don't think it's GPU-specific, it does happen with DRI disabled, but to be sure, my GPU is GM45, managed by i915.