Changing a project follower into a project user

Changing a project follower into a project user

I have a project which a portal user was following. Now the situation has changed where this user needs to be a actual project team member. However, if I try to add this user it gives me an error saying - (User already added as Follower to this project).
Is the only way to fix this for the user to unfollow and then get added as a project user? Or is there a simpler way (without the project manager having to ask the user to unfollow first) for this to be done?

Thanks,
Menno