```ruby
module DeviseInvitable
  module Mailer

    # Deliver an invitation email
    def invitation_instructions(record, opts={})
      devise_mail(record, :invitation_instructions, opts)
    end
  end
end
```

Make it play nice with older versions of devise
user
```ruby
require 'devise/version'

module DeviseInvitable
  module Mailer

    # Deliver an invitation email
    def invitation_instructions(record, opts={})
      # optional arguments introduced in Devise 2.2.0, remove check once support for < 2.2.0 is dropped.
      if Gem::Version.new(Devise::VERSION.dup) < Gem::Version.new('2.2.0')
        devise_mail(record, :invitation_instructions)
      else
        devise_mail(record, :invitation_instructions, opts)
      end
    end
  end
end
```
assistant