Can't access methods within a Sinatra::Base class

test.txt

$ irb
2.0.0-p353 :001 > require 'sinatra/base'
 => true 
2.0.0-p353 :002 > class PlainClass
2.0.0-p353 :003?>     def say_cheese
2.0.0-p353 :004?>         "cheese"
2.0.0-p353 :005?>       end
2.0.0-p353 :006?>   end
 => nil 
2.0.0-p353 :007 > class SinatraClass < Sinatra::Base
2.0.0-p353 :008?>     def say_cheese
2.0.0-p353 :009?>         "cheese"
2.0.0-p353 :010?>       end
2.0.0-p353 :011?>   end
 => nil 
2.0.0-p353 :012 > PlainClass.new.say_cheese
 => "cheese" 
2.0.0-p353 :013 > SinatraClass.new.say_cheese
NoMethodError: undefined method `say_cheese' for #<Sinatra::Wrapper:0x8e4061c>
	from (irb):13
	from /home/raw/.rvm/rubies/ruby-2.0.0-p353/bin/irb:12:in `<main>'
2.0.0-p353 :014 >