Well, I drank it like a normal beer, so maybe that was the problem as well.
Anyway, this is likely a one-time thing anyway, because my roommate brought it with him from when he went beer shopping in the Czech Republic - I don't think I've ever seen beer beyond the 6.5% in German shops (though, to be fair, I'm sure that there are dedicated beer shops where I could find stuff like that if I were to look).