Is it permissible for a pilgrim in a state of ihram to cover his head while sleeping?

If the pilgrim (muhrim) is female, she is permitted to cover her head. However, if he is a male, he is not allowed to do so, neither while asleep nor while awake. If a male pilgrim covers his head while asleep and then wakes up, he must uncover his head, and there is no penalty upon him, because the pen is lifted from the sleeper.