Celluloid futures playing up?

future_sample.rb

require 'celluloid'
require 'celluloid/future'

def pusher(future)
  sleep 5
  future.signal 'Wibble'
end

def puller(future)
  puts "Pulled: #{future.value}"
end

future = Celluloid::Future.new

t1 = Thread.new {
  begin
    puller(future)
  rescue Exception => e
    puts "Exception raised: #{e.message}\n    #{e.backtrace.join("\n    ")}"
  end
}
t2 = Thread.new {
  begin
    pusher(future)
  rescue Exception => e
    puts "Exception raised: #{e.message}\n    #{e.backtrace.join("\n    ")}"
  end
}

t1.join
t2.join

%%

Output:
/usr/bin/ruby1.9.3 -e $stdout.sync=true;$stderr.sync=true;load($0=ARGV.shift) /home/langfords/Dropbox/work/clouddeploy/src/future_sample.rb
Exception raised: undefined method `value' for "Wibble":String
    /home/langfords/.gem/ruby/1.9.1/gems/celluloid-0.15.1/lib/celluloid/future.rb:104:in `value'
    /home/langfords/.gem/ruby/1.9.1/gems/celluloid-0.15.1/lib/celluloid/future.rb:68:in `value'
    /home/langfords/Dropbox/work/clouddeploy/src/future_sample.rb:10:in `puller'
    /home/langfords/Dropbox/work/clouddeploy/src/future_sample.rb:17:in `block in <top (required)>'

%