Bug in pp library

ruby -r pp -e 'PP.singleline_pp({ 1 => 1})'

usr/lib/ruby/1.9/pp.rb:221:in `pp_hash': undefined method `seplist' for 
#<PP::SingleLine:0x38d5f8> (NoMethodError)
         from /usr/lib/ruby/1.9/pp.rb:220:in `group'
         from /usr/lib/ruby/1.9/pp.rb:220:in `pp_hash'
         from /usr/lib/ruby/1.9/pp.rb:293:in `pretty_print'
         from /usr/lib/ruby/1.9/pp.rb:185:in `pp'
         from /usr/lib/ruby/1.9/pp.rb:185:in `group'
         from /usr/lib/ruby/1.9/pp.rb:185:in `pp'
         from /usr/lib/ruby/1.9/pp.rb:147:in `singleline_pp'
         from /usr/lib/ruby/1.9/pp.rb:147:in `guard_inspect_key'
         from /usr/lib/ruby/1.9/pp.rb:147:in `singleline_pp'
         from -e:1

Cheers

Dave