Bukkit

I have the issue where a player is added to group called "Voter" that contains WorldEdit permission for 1 day. After one day of using WorldEdit, this certain player's Voter group will be expired. In this case, it expires but is not removed from the temporary group. I tested several more and noticed that the format "/permissions group <group> add <player> [<duration/timestamp>]" does not "expire and remove the player from group" So I used /permissions cleanup. It was successful, but it still didnt remove the player from "Voter" group even though it is expired. How can I fix this? Thanks!