Can't install gem

[oriolgual]

$ gem install capybara-webkit
Building native extensions.  This could take a while...
ERROR:  Error installing capybara-webkit:
ERROR: Failed to build gem native extension.

    /Users/oriol/.rvm/rubies/ruby-1.9.2-p180/bin/ruby extconf.rb
    /Users/oriol/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems.rb:407:in `bin_path': can't find gem rake ([">= 0"]) with executable rake (Gem::GemNotFoundException)
    from /Users/oriol/.rvm/gems/ruby-1.9.2-p180@global/bin/rake:19:in `<main>'


Gem files will remain installed in /Users/oriol/.rvm/gems/ruby-1.9.2-p180@global/gems/capybara-webkit-0.1.5 for inspection.
Results logged to /Users/oriol/.rvm/gems/ruby-1.9.2-p180@global/gems/capybara-webkit-0.1.5/./gem_make.out

Using rubygems 1.7.2 (also tried with 1.7.1) and qt installed with homebrew (and rake is installed)

[oriolgual]

Solved with $ rvm exec gem install capybara-webkit

Sorry, it's not solved. With rvm exec installed OK with jruby 1.6, rbx and 1.8.7 but fails with 1.9.2 :(

[oriolgual]

Didn't read well issue #6, closing as duplicate.