- belongs_to :user, :class_name => "User", :foreign_key => :user_id
- belongs_to :creator, :class_name => "User", :foreign_key => :creator_id
- belongs_to :revoker, :class_name => "User", :foreign_key => :revoker_id
+ belongs_to :user, :class_name => "User"
+ belongs_to :creator, :class_name => "User"
+ belongs_to :revoker, :class_name => "User", :optional => true