ActiveMailer syntax error

application_mailer.rb

class ApplicationMailer < ActionMailer::Base
  def welcome_email(instructor)
    recipients  instructor.email
    from        APP_CONFIG['system_email_address']
    subject     "Welcome to #{APP_CONFIG['application_name']}. Thank you for registering."
    sent_on     Time.now
    body        {:instructor => instructor}
  end
end

gistfile1.txt

suki[SimNotify] (feature/mailer)$ script/console 
Loading development environment (Rails 2.3.8)
>> ApplicationMailer.deliver_welcome_email("test")
SyntaxError: /Users/suki/source/SimNotify/app/models/application_mailer.rb:7: syntax error, unexpected tASSOC, expecting '}'
    body        {:instructor => instructor}
                               ^
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:380:in `load_without_new_constant_marking'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:380:in `load_file'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:521:in `new_constants_in'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:379:in `load_file'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:259:in `require_or_load'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:425:in `load_missing_constant'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:80:in `const_missing'
        from /Library/Ruby/Gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:92:in `const_missing'
        from (irb):1
>> 

Attempting to use the examples from Action Mailer Basics will cause the above error. Instead remove the curly brackets:

body           :instructor => instructor

This will work. I have no idea why the docs say otherwise.