Using Pundit and ActiveAdmin

Hello, I'm using pundit with active admin and getting this error message

Pundit::NotDefinedError at /admin
unable to find scope Admin::AdminUserPolicy::Scope for [:admin, AdminUser(id: integer, email: string, encrypted_password: string, reset_password_token: string, reset_password_sent_at: datetime, remember_created_at: datetime, created_at: datetime, updated_at: datetime)]

What do I need to do to solve this situation ?

Thanks for your help!