diff --git a/Gemfile b/Gemfile
index 7d0dd2e..932d740 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,6 +3,7 @@ source 'https://rubygems.org'
 gem 'minitest', '~> 5.21.2'
 gem 'mocha', '~> 2.1.0'
 gem 'nokogiri', '~> 1.16.2'
+gem 'rackup', '~> 2.1.0'
 gem 'rake', '~> 13.0.0'
 gem 'rubocop', '~> 1.60'
 gem 'sinatra', '~> 4.0.0'