Rake interrupted! uninitialized constant Object :: Country, why is the model not visible?

Question

I have rails 3.1, I'm trying to fill in the data seeds.rb I have a Country model that wraps to the country table

But it seems that the rails cannot see the country model from seeds.rb I get this error:

 rake aborted! uninitialized constant Object::Country Tasks: TOP => db:seed 

My seeds.rb file looks like this:

 # encoding: UTF-8 Country.delete_all 

my country model:

 class Country < ActiveRecord::Base has_many :students has_many :instructors end 

any idea please?

EDIT

I am in a development environment, config.threadsafe!