/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:60:in `require': /var/lib/gems/1.9.1/gems/ruby-debug-base19-0.11.25/lib/ruby_debug.so: undefined symbol: ruby_current_thread - /var/lib/gems/1.9.1/gems/ruby-debug-base19-0.11.25/lib/ruby_debug.so (LoadError)
    f  r om /usr/lib/ruby/1.9.1/ rubygems/custom_require.rb:60:in `rescue in require'
    f  r om /usr/lib/ruby/1.9.1/ rubygems/custom_require.rb:35:in `require'
    f  r om /var/lib/gems/1.9.1/ gems/ruby-debug-base19-0.11.25/lib/ruby-debug-base.rb:1:in `<top (required)>'
    f  r om /usr/lib/ruby/1.9.1/ rubygems/custom_require.rb:36:in `require'
    f  r om /usr/lib/ruby/1.9.1/ rubygems/custom_require.rb:36:in `require'
    f  r om /var/lib/gems/1.9.1/ gems/ruby-debug19-0.11.6/cli/ruby-debug.rb:5:in `<top (required)>'
    f  r om /var/lib/gems/1.9.1/ gems/ruby-debug19-0.11.6/bin/rdebug:108:in `require_relative'
    f  r om /var/lib/gems/1.9.1/ gems/ruby-debug19-0.11.6/bin/rdebug:108:in `<top (required)>'
    f  r om /usr/local/bin/rdebu g:23:in `load'
    f  r om /usr/local/bin/rdebu g:23:in `<main>'