diff --git a/Gemfile b/Gemfile
index 12a9ce1..ac0d2fb 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,7 +13,7 @@ group :development, :test do
 end
 
 group :test do
-  gem 'rack', '< 2', platform: [:mri_21, :mri22]
+  gem 'rack', '< 2', platform: [:mri_21, :mri_22]
   gem 'rack', '>= 2', platform: :mri_23
 
   gem "coveralls", "~>0.8", require: false