Rails 3 and Rack compatibility

hi there,

Is the latest Rails 3 compatible with Rack 1.0.0 ?
I get this error today:

/config.ru:2:in `block in parse_config': undefined method
`expand_path' for Rack::File:Class (NoMethodError)
  from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.0.0/lib/rack/builder.rb:29:in
`instance_eval'
  from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.0.0/lib/rack/builder.rb:29:in
`initialize'

I generated the rails application from scratch.

Kind regards,

I think it isn't:

http://github.com/rails/rails/commit/ef70ad5538c4ce02c4d31ef01a8db6b55c837571