diff --git a/Gemfile b/Gemfile
index 976ff1b..c49be77 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,6 +5,7 @@ source 'http://rubygems.org'
 group :development do
   gem 'rake'
   gem 'rspec', '~> 3.7'
+  gem 'webrick'
 
   # Use same version as Code Climate for consistency with CI
   # https://github.com/codeclimate/codeclimate-rubocop/blob/master/Gemfile.lock