Apparently ActiveAdmin does not like the default setting. Rails documentation advices to change the default name anyway, so I did by adding this to my migration file
class CreateRoles < ActiveRecord::Migration
def change
create_table :roles do |t|
# some other attributes
t.string :object_type #this will be your 'type' column from now on
t.timestamps
end
add_index :roles, :object_type
end
end
Then on the role class I added
set_inheritance_column 'object_type'
Surprisingly, this change was not getting any effect after doing a rake db:migrate. So I did a db:drop, db:reset, db:migrate and db:seed and everything started working fine.
Side note: Bare in mind that if you are doing a 'big bang' approach on development (you shouldn't) you can lock yourself out of the app when roles start working.