rbx loader.rb error

$ rbx loader.rb 
An exception occurred running loader.rb
    Coercion error: nil.to_str => String failed (TypeError)

Backtrace:
                        Type.coerce_to at kernel/common/type.rb:22
  Kernel(Rubinius::CodeLoader)#StringValue at kernel/common/kernel.rb:112
       Rubinius::CodeLoader#initialize at kernel/common/codeloader.rb:22
                       main.__script__ at loader.rb:3
      Rubinius::CodeLoader#load_script at kernel/delta/codeloader.rb:67
      Rubinius::CodeLoader.load_script at kernel/delta/codeloader.rb:91
               Rubinius::Loader#script at kernel/loader.rb:435
                 Rubinius::Loader#main at kernel/loader.rb:527
                 Rubinius::Loader.main at kernel/loader.rb:553
                     Object#__script__ at kernel/loader.rb:565

Caused by: no method 'to_str' on nil:NilClass. (NoMethodError)

Backtrace:
  Kernel(NilClass)#to_str (method_missing) at kernel/delta/kernel.rb:85
                        Type.coerce_to at kernel/common/type.rb:20
  Kernel(Rubinius::CodeLoader)#StringValue at kernel/common/kernel.rb:112
       Rubinius::CodeLoader#initialize at kernel/common/codeloader.rb:22
                       main.__script__ at loader.rb:3
      Rubinius::CodeLoader#load_script at kernel/delta/codeloader.rb:67
      Rubinius::CodeLoader.load_script at kernel/delta/codeloader.rb:91
               Rubinius::Loader#script at kernel/loader.rb:435
                 Rubinius::Loader#main at kernel/loader.rb:527
                 Rubinius::Loader.main at kernel/loader.rb:553
                     Object#__script__ at kernel/loader.rb:565