another riddle

After you die, your spirit reaches a room with two identical doors, and two guards guarding each one. You know that one is the door to heaven, and the other one is the door to hell, you also know that one of the guards always lies, and the other one always tells the truth, but you don't know which one, nor what door they are guarding.

You can ask one question to one of the guards, what do you ask to make sure you choose the door to heaven?