I've never liked it when the Two Brothers riddles are worded like this. Either the "always telling the truth" brother is the one saying the riddle, and you know who to ask which door is safe or its the "always lying" brother, in which you don't know what the actual riddle is (as the one they just told you is a lie) and both doors probably lead to the certain death.

(I should probably add that I get the refrence in the post, I'm just being nitpicky)