Error: histogram.rb does not want to work

Trying to run the histogram.rb examples (the other work fine by the way)

rb histogram.rb

Error:

ruby_gnuplot-master/lib/gnuplot.rb:204:in `style': wrong number of arguments (given 1, expected 0) (ArgumentError)

The code in question is:

def style &blk
  s = Style.new &blk
  @styles << s
  s
end

Unfortunately I do not know how to fix the above.