diff --git a/em-http-request.gemspec b/em-http-request.gemspec
index 00937b5a..e6e26714 100644
--- a/em-http-request.gemspec
+++ b/em-http-request.gemspec
@@ -23,7 +23,7 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency 'mongrel', '~> 1.2.0.pre2'
   s.add_development_dependency 'multi_json'
-  s.add_development_dependency 'rack'
+  s.add_development_dependency 'rack', '< 2.0'
   s.add_development_dependency 'rake'
   s.add_development_dependency 'rspec'