Middle click paste does not trigger URL match/cleanup

Using middle click to paste a URL does not trigger the URL match/cleanup in the same way it does when using ctrl-v. It does run later at various points, but I expect it to clean up the URL as soon as I paste so that I can check it looks ok before submitting it. It doesn't though, so I end up pressing space or something just to trigger it, so that I can check that it looks ok.

Reproducible in Opera 12.02 and Firefox 15.0.1 in Linux