Spree state machine missing callback in production mode

I have written an order decorator, app/models/spree/order_decorator.rb:

module Spree
  module OrderDecorator
    def self.prepended(base)
      base.whitelisted_ransackable_attributes += %w[synced_with_erp]
    end

    def update_user_was_purchased
      user.update_column(:was_purchase, true) if user
    end
  end
end
::Spree::Order.prepend Spree::OrderDecorator if ::Spree::Order.included_modules.exclude?(Spree::OrderDecorator)
Spree::Order.state_machine.after_transition to: :complete, do: :update_user_was_purchased

When I run this code in development console:

Spree::Order.state_machine.callbacks[:after].find { |callback| 
  callback.instance_variable_get("@methods").include?(:update_user_was_purchased)
}

it returns the callback object, as expected.

However, when i run it in console on a production server it returns nil, and hence it does not work.