Gettext support in ruby can not be used

When a ruby application 'require' the gettext support it don't work and tell use something like this:
/usr/lib/ruby/1.8/gettext/locale_default.rb:12:in `require': no such file to load -- gettext/_locale (LoadError)
        from /usr/lib/ruby/1.8/gettext/locale_default.rb:12
        from /usr/lib/ruby/1.8/gettext/locale.rb:15
        from /usr/lib/ruby/1.8/gettext.rb:18
        from /usr/bin/alexandria:6