New Post: FollowersCount bigger then 0 but FollowerIds list is null

Hi there,
I have a problem with getting followerIds list. Here Is my code,

List<long> MyFollowersIds = AccountUser.FollowerIds;

AccountUser is IUser object and FollowersCount is 58. But FollowerIds list is null.

Anyone any idea?

By the way I am very new in Tweetinvi aproximately 2 hours.