sinatra jruby glassfish

1. I startup via jruby -S glassfish -l
2. I get this error:
SEVERE: undefined method `disable' for main:Object from <script>:1
com.sun.grizzly.jruby.rack.RackInitializationException: undefined
method `disable' for main:Object from <script>:1

3.I these 2 files below in my cwd.
--- config.ru ---
require 'rubygems'
gem 'sinatra', '>=0'
require 'rack/handler/grizzly'
require 'myapp'
PATH = 'myapp.rb'
set :server, 'grizzly'
set :app_file, PATH
set :adapter, 'grizzly'
MyApp.run  # was Sinatra.run b4subclass
$grizzly_rack_app

-- myapp.rb ---

require 'rubygems'

require 'sinatra/base' # was 'sinatra' b4 run

class MyApp < Sinatra::Base
  get "/" do
      'Hello world!'
  end
end