What does “WARN Could not determine content-length of response body.” mean and how to I get rid of it?

Question

Since upgrading to Rails 3.1 I\'m seeing this warning message in my development log:

WARN Could not determine content-length of response body. Set co

Answer 1

Just explicitly adding the Gem to the Gemfile got rid of the warning messages for me:

group :development do
  gem 'webrick', '~> 1.3.1'
end