Heh, the memories...
We had a character in one campaign who would "never tell a lie". The tricky part was that he had also a secret identity - he never wanted to talk about it.
So regularly, he returned from some dark corner and one of us asked him what he had been doing there...
Us: Hey, you're back! Where have you been?
Him: Err...from a back-alley.
Us: What have you been doing there? (grin)
Him: I won't tell you anything about this.
Us: Aw, come on! We've seen your contact!
Him: Goddammit, I won't tell you ANYTHING!
Man, that was fun. He got angry so easily.
And yeah, I like your solution too.