diff --git a/omniauth-twitter.gemspec b/omniauth-twitter.gemspec
index 85d6f79..fcdb38b 100644
--- a/omniauth-twitter.gemspec
+++ b/omniauth-twitter.gemspec
@@ -18,5 +18,6 @@
   s.require_paths = ["lib"]
   s.required_ruby_version = Gem::Requirement.new('>= 1.9.3')
   s.add_dependency 'omniauth-oauth', '~> 1.1'
+  s.add_dependency 'rack'
   s.add_development_dependency 'bundler', '~> 1.0'
 end