RuntimeError on JRuby 1.6.7 on Win7 32bit

[jonforums]

C:\Users\Jon\Downloads\temp>jruby --version
jruby 1.6.7 (ruby-1.8.7-p357) (2012-02-22 3e82bc8) (Java HotSpot(TM) Client VM 1.7.0_03) [Windows 7-x86-java]

C:\Users\Jon\Downloads\temp>nabit ftp://sourceware.org/pub/libffi/libffi-3.0.10.tar.gz
ERROR: can't convert nil into String
RuntimeError: Failed to download file
   ftp_download at C:/jruby/lib/ruby/gems/1.8/gems/nabit-0.2.0/lib/nabit/downloader.rb:170
  download_file at C:/jruby/lib/ruby/gems/1.8/gems/nabit-0.2.0/lib/nabit/downloader.rb:25
            run at C:/jruby/lib/ruby/gems/1.8/gems/nabit-0.2.0/bin/nabit:30
         (root) at C:/jruby/lib/ruby/gems/1.8/gems/nabit-0.2.0/bin/nabit:40
           load at org/jruby/RubyKernel.java:1058
         (root) at C:\jruby\bin\nabit:23