My API Stripe keys not working in production?

Question

I have an app where i am trying to integrate stripe api. While following a certain tutorial i managed to configure my stripe keys as shown below.

In config/application.yml (figaro)

development:
  stripe_secret_key: sk_test_******************
  stripe_publishable_key: pk_test_******************

production:
  stripe_secret_key: sk_test_******************
  stripe_publishable_key: pk_test_******************

Then in config/initializers/stripe.rb i have

Rails.configuration.stripe = {
    :publishable_key => ENV['stripe_publishable_key'],
    :secret_key      => ENV['stripe_secret_key']
}

Stripe.api_key = Rails.configuration.stripe[:secret_key]

Everything works fine in development, however, when i deploy my app to heroku i get the error "You did not set a valid publishable key". Can someone advise, what is it i am doing wrong? I am still working with test mode.