I am extending a class (which is in a plugin) by including a module, this is done in an initializer.
require \'qwerty/core/user\' User.send :include, Qwerty::Co
Why do you use initializers to include functionality?
Try the following instead:
require 'qwerty/core/user' class User < ActiveRecord::Base include Qwerty::Core::Extensions::User # bla bla end