save_and_open_page not referencing html file correctly

I’ve added the save_and_open_page as an After hook as per page 151, but the browser opens the saved page incorrectly. Rather than opening, eg.

file:///Users/michaelallan/scratch/cucumber-book/atm/capybara-201302101633346148374723.html

... it opens this instead:

http://capybara-201302101633346148374723.html/

... which of course doesn’t exist.

I’m using rvm and bundler on Mac OS X 10.6.8, with Safari set as my default browser. I’m also using slightly different gem versions that those specified, ie. the ones current as of today per this Gemfile:

source :rubygems

gem 'sinatra', '1.3.4'

group :development do
  gem 'rspec', '2.0.1'
  gem 'cucumber', '1.2.1'
  gem 'capybara', '2.0.2'
  gem 'launchy', '2.2.0'
end

Apologies if this is a silly question, but I’ve not had any luck googling for an answer. Thanks for any suggestions, and I’m really enjoying the book :-)