diff --git a/rack-test.gemspec b/rack-test.gemspec
index 6f295354..8a25806e 100644
--- a/rack-test.gemspec
+++ b/rack-test.gemspec
@@ -21,6 +21,7 @@ request helpers feature.
   s.require_paths = ['lib']
   s.files = `git ls-files -- lib/*`.split("\n") +
             %w[History.md MIT-LICENSE.txt README.md]
+  s.required_ruby_version = ">= 2.2.2"
   s.add_dependency 'rack', '>= 1.0', '< 3'
   s.add_development_dependency 'rake', '~> 12.0'
   s.add_development_dependency 'rspec', '~> 3.6'