Sinatra + mumboe-soap4r + ruby1.9.1 problem

Hi 2 all, i have following problem - simple ruby application with soap
and sinatra

require ‘rubygems’
require ‘sinatra’
gem ‘mumboe-soap4r’
require ‘soap/rpc/driver’
get ‘/’ do
‘just text’

When i’m trying to reach this page via browser i see

"Internal Server Error
undefined method `split’ for nil:NilClass "

webrick error (because of Content-type=nil)
but if you comment out soap import (require ‘soap/rpc/driver’) all works
fine…seems that soap just override webrick respond and produce an
error. Any thoughts?