ao tentar executar o seguinte comando recebo um erro:

jekyll new myblog

E o erro é o seguinte:

/var/lib/gems/1.8/gems/commander-4.1.5/lib/commander/runner.rb:365:in `require_program': program version required (Commander::Runner::CommandError)
from /var/lib/gems/1.8/gems/commander-4.1.5/lib/commander/runner.rb:364:in `each'
from /var/lib/gems/1.8/gems/commander-4.1.5/lib/commander/runner.rb:364:in `require_program'
from /var/lib/gems/1.8/gems/commander-4.1.5/lib/commander/runner.rb:52:in `run!'
from /var/lib/gems/1.8/gems/commander-4.1.5/lib/commander/delegates.rb:7:in `run!'
from /var/lib/gems/1.8/gems/commander-4.1.5/lib/commander/import.rb:10
from /usr/local/bin/jekyll:19
/usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require': no such file to load -- json (LoadError)
from /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /var/lib/gems/1.8/gems/jekyll-1.3.0/bin/../lib/jekyll/filters.rb:2
from /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /var/lib/gems/1.8/gems/jekyll-1.3.0/bin/../lib/jekyll.rb:43
from /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
from /usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `require'
from /var/lib/gems/1.8/gems/jekyll-1.3.0/bin/jekyll:7
from /usr/local/bin/jekyll:19:in `load'
from /usr/local/bin/jekyll:19

Eu corro ElementaryOS e tenho o ruby-dev (1.9.1) também instalado.