Ironruby core - Feb 2010 - Bug in delete_at??

I think there might be a bug in the way delete_at works.

a = [1,2]
a.delete_at(1)
=> 2
a.delete_at(1)
RangeError: Specified argument was out of the range of valid values.
Parameter name: index
        from :0:in `delete_at''
        from (irb):38
        from :0:in `eval''
        from workspace.rb:80:in `evaluate''
        from context.rb:217:in `evaluate''
        from irb.rb:147:in `eval_input''
        from irb.rb:257:in `signal_status''
        from irb.rb:146:in `eval_input''
        from ruby-lex.rb:230:in `each_top_level_statement''
        from :0:in `loop''
        from c:/IronRuby/lib/ruby/1.8/irb.rb:146:in `eval_input''
        from c:/IronRuby/lib/ruby/1.8/irb.rb:70:in `start''
        from :0:in `catch''
        from c:/IronRuby/lib/ruby/1.8/irb.rb:69:in `start''
        from c:/IronRuby/bin/iirb:13
        from :0:in `catch''
a.delete_at(2)
=>nil

The a.delete_at(1) should return nil, but it is throwing an exception.  Is that
correct?

Thanks,
Randall