Links in QMessageBox are no longer clickable

In an earlier version of Qt (it must have been around Qt 4.5), it was possible to set the Text of a QMessageBox, for example, to "I am <a href='http://google.de'>a link</a>", and then one could click the link after the box opened, to get a browser in the given webpage, or to open an email (for mailto: links). For that reason I used a QMessageBox for the about dialogue of my applications, which make heavy use of that feature.

Now I recently noticed, by pure coincidence, that somewhere on the way to Qt 4.7.3 which I am using now, this behaviour was changed. Links still show up blue and underlined, but they are not clickable. This totally breaks the about box of my applications, and it breaks the backwards compatibility promise of Qt. I can not find a way to change the QMessageBox behaviour, so to fix this I would have to create the about dialogue from scratch.

You can find a simple demo application with such a non-functional link attached.