Philips Econic 5W - glass breaks

A few hours ago I was happy that it came with a real glass dome. Now I've discovered this nasty crack. I don't know if it was there initially or if it developed due to thermal stress. I definitely don't remember dropping it or hitting it with something hard. I'll do a little 'burn-in' test and see if it grows any further, or if the other one gets such a crack as well.

It doesn't affect the bulbs function yet, but I'm not fond of glass shrapnels. The only positive side effect of the dome breaking would be that I could have a look inside ;-)