webrick fails for pry.github.com

gistfile1.txt

spooner@spooner-VirtualBox:~/RubymineProjects/pry.github.com$ foreman start
16:26:28 jekyll.1   | started with pid 15708
16:26:29 compass.1  | started with pid 15711
16:26:33 jekyll.1   | Configuration from ./_config.yml
16:26:33 jekyll.1   | Auto-regenerating enabled: ./ -> ./_site
16:26:33 jekyll.1   | [2011-11-29 16:26:33] regeneration: 32 files changed
16:26:34 compass.1  | >>> Change detected to: style.scss
16:26:34 jekyll.1   | [2011-11-29 16:26:34] INFO  WEBrick 1.3.1
16:26:34 jekyll.1   | [2011-11-29 16:26:34] INFO  ruby 1.9.2 (2011-02-18) [x86_64-linux]
16:26:34 jekyll.1   | /usr/share/ruby-rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/utils.rb:63:in `getaddrinfo': getaddrinfo: Servname not supported for ai_socktype (SocketError)
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/utils.rb:63:in `create_listeners'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/server.rb:74:in `listen'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/server.rb:62:in `initialize'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/webrick/httpserver.rb:24:in `initialize'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/gems/ruby-1.9.2-p180/gems/jekyll-0.11.0/bin/jekyll:271:in `new'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/gems/ruby-1.9.2-p180/gems/jekyll-0.11.0/bin/jekyll:271:in `<top (required)>'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/gems/ruby-1.9.2-p180/bin/jekyll:19:in `load'
16:26:34 jekyll.1   |   from /usr/share/ruby-rvm/gems/ruby-1.9.2-p180/bin/jekyll:19:in `<main>'
16:26:34 jekyll.1   | process exiting
16:26:34 compass.1  | process terminated
16:26:34 system     | sending SIGTERM to all processes
16:26:35 compass.1  | SignalException on line ["40"] of /usr/share/ruby-rvm/gems/ruby-1.9.2-p180/gems/sass-3.1.10/lib/sass/cache_stores/filesystem.rb: SIGTERM
16:26:35 compass.1  | Run with --trace to see the full backtrace
16:26:35 compass.1  | process exiting

There is no problem with directly calling that utility method, however (with identical params):

$ ruby -rwebrick -ve 'p WEBrick::Utils::create_listeners(nil, 5000)'
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]
[#<TCPServer:fd 3>]