Backtrace

NoMethodError: undefined method `downcase' for nil:NilClass
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/request.rb:44:in `media_type'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/request.rb:114:in `form_data?'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/request.rb:144:in `POST'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/request.rb:165:in `params'
	/usr/local/lib/ruby/gems/1.8/gems/sinatra-1.0/lib/sinatra/base.rb:408:in `call!'
	/usr/local/lib/ruby/gems/1.8/gems/sinatra-1.0/lib/sinatra/base.rb:399:in `call'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/showexceptions.rb:24:in `call'
	/usr/local/lib/ruby/gems/1.8/gems/sinatra-1.0/lib/sinatra/base.rb:979:in `call'
	/usr/local/lib/ruby/gems/1.8/gems/sinatra-1.0/lib/sinatra/base.rb:1005:in `synchronize'
	/usr/local/lib/ruby/gems/1.8/gems/sinatra-1.0/lib/sinatra/base.rb:979:in `call'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/content_length.rb:13:in `call'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/chunked.rb:15:in `call'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/connection.rb:76:in `pre_process'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/connection.rb:74:in `catch'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/connection.rb:74:in `pre_process'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/connection.rb:57:in `process'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/connection.rb:42:in `receive_data'
	/usr/local/lib/ruby/gems/1.8/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run_machine'
	/usr/local/lib/ruby/gems/1.8/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/backends/base.rb:57:in `start'
	/usr/local/lib/ruby/gems/1.8/gems/thin-1.2.5/lib/thin/server.rb:156:in `start'
	/usr/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/handler/thin.rb:14:in `run'
	/usr/local/lib/ruby/gems/1.8/gems/sinatra-1.0/lib/sinatra/base.rb:946:in `run!'
	./server:41

rack_content_type_patch.rb

class Rack::Request
  def content_type
    content_type = @env['CONTENT_TYPE']
    if content_type == ''
      nil
    else
      content_type
    end
  end
end

Sample s3sync s3cmd request

s3sync's s3cmd actually sends a request like this:

PUT /path/file? HTTP/1.0
Host: 127.0.0.1:4567
Connection: close
Accept: */*
Content-Type: 
Date: Thu, 22 Jul 2010 19:31:10 GMT
Content-Length: 48