Ruby Debug for Rails3

                     gem 'ruby-debug19'   #for ruby 1.9
instead of   #gem 'ruby-debug'

I tried to put ruby-debug gems for my rails app,
  gem 'ruby-debug'

and it turned up as an error:
Installing linecache (0.43) with native extensions /home/wei/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/site_ruby/1.9.1/rubygems/installer.rb:533:in `rescue in block in build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

        /home/wei/.rvm/rubies/ruby-1.9.2-p136/bin/ruby extconf.rb
Can't handle 1.9.x yet

After changing to ruby-debug19, it works.
Installing linecache19 (0.5.12) with native extensions