rbx failure when running `defined?(__ENCODING__)`

stack_trace

An exception occurred running /home/travis/.rvm/gems/rubinius-2.0.0-weekly20130906-d19@global/gems/rake-10.1.0/lib/rake/rake_test_loader.rb
    /home/travis/build/driv3r/simple-rss/lib/simple-rss/parser.rb:3: defined? passed an unrecognized expression (Exception)

Backtrace:
        Rubinius.unrecognized_defined at kernel/delta/rubinius.rb:242
                    Object#__script__ at lib/simple-rss/parser.rb:3
         Rubinius::CodeLoader.require at kernel/common/codeloader.rb:232
               Kernel(Object)#require at kernel/common/kernel.rb:635
                    Object#__script__ at lib/simple-rss.rb:5
         Rubinius::CodeLoader.require at kernel/common/codeloader.rb:232
               Kernel(Object)#require at kernel/common/kernel.rb:635
                    Object#__script__ at test/test_helper.rb:4
         Rubinius::CodeLoader.require at kernel/common/codeloader.rb:232
               Kernel(Object)#require at kernel/common/kernel.rb:635
                    Object#__script__ at test/base/base_test.rb:2
         Rubinius::CodeLoader.require at kernel/common/codeloader.rb:232
               Kernel(Object)#require at kernel/common/kernel.rb:635
            { } in Object#__script__ at /home/travis/.rvm/gems
                                        /rubinius-2.0.0-weekly20130906-d19@global
                                        /gems/rake-10.1.0/lib/rake
                                        /rake_test_loader.rb:10
                           Array#each at kernel/bootstrap/array.rb:68
            { } in Object#__script__ at /home/travis/.rvm/gems
                                        /rubinius-2.0.0-weekly20130906-d19@global
                                        /gems/rake-10.1.0/lib/rake
                                        /rake_test_loader.rb:9
    { } in Enumerable(Array)#find_all at kernel/common/enumerable.rb:232
                           Array#each at kernel/bootstrap/array.rb:68
  Enumerable(Array)#select (find_all) at kernel/common/enumerable.rb:230
                   Object#__script__ at /home/travis/.rvm/gems
                                        /rubinius-2.0.0-weekly20130906-d19@global
                                        /gems/rake-10.1.0/lib/rake
                                        /rake_test_loader.rb:4
     Rubinius::CodeLoader#load_script at kernel/delta/codeloader.rb:68
     Rubinius::CodeLoader.load_script at kernel/delta/codeloader.rb:111
              Rubinius::Loader#script at kernel/loader.rb:648
                Rubinius::Loader#main at kernel/loader.rb:847
rake aborted!
Command failed with status (1): [ruby -I"lib:test" -I"/home/travis/.rvm/gems/rubinius-2.0.0-weekly20130906-d19@global/gems/rake-10.1.0/lib" "/home/travis/.rvm/gems/rubinius-2.0.0-weekly20130906-d19@global/gems/rake-10.1.0/lib/rake/rake_test_loader.rb" "test/**/*_test.rb" ]
kernel/bootstrap/proc.rb:22:in `call'
kernel/bootstrap/proc.rb:22:in `call'
kernel/bootstrap/array.rb:68:in `each'
kernel/bootstrap/array.rb:68:in `each'
kernel/bootstrap/array.rb:68:in `each'
kernel/common/kernel.rb:584:in `load'
kernel/common/block_environment.rb:55:in `call_on_instance'
kernel/common/eval.rb:74:in `eval'
/home/travis/.rvm/gems/rubinius-2.0.0-weekly20130906-d19/bin/ruby_noexec_wrapper:14:in `__script__'
kernel/delta/codeloader.rb:68:in `load_script'
kernel/delta/codeloader.rb:111:in `load_script'
kernel/loader.rb:648:in `script'
kernel/loader.rb:847:in `main'
Tasks: TOP => default => test
(See full trace by running task with --trace)