Cucumber output bug

my_steps.rb

And(/^do a thing$/) do
  foo = 'a'
  puts foo # Should output 'a'

  foo.upcase!
  puts foo # Should output 'A'

  foo = 'b'
  puts foo # Should output 'b'
end

my_test_feature.feature

Feature:

  Scenario: 
    * do a thing

pure_ruby.rb

foo = 'a'
puts foo # Should output 'a'

foo.upcase!
puts foo # Should output 'A'

foo = 'b'
puts foo # Should output 'b'