Using the pound key as a valid choice in a Tropo ask

More of a reminder to myself, but might be useful for others, as I found this through trial and error. We have an ask in our call flow that wants to capture the pound key (#) as a valid choice. Seems easy enough, just add the pound symbol '#' as a choice to the choices array. But that alone doesn't work. You also have to assign a different terminator to the ask (e.g. '*'). You won't actually use the terminator, but reassigning the terminator to something other than '#' seems to free '#' up to be used as a valid choice.