diff --git a/http-cookie.gemspec b/http-cookie.gemspec
index b680b70..f9208b1 100644
--- a/http-cookie.gemspec
+++ b/http-cookie.gemspec
@@ -24,4 +24,5 @@ Gem::Specification.new do |gem|
 
   gem.add_runtime_dependency("domain_name", ["~> 0.5"])
   gem.add_development_dependency("bundler", [">= 1.2.0"])
+  gem.add_development_dependency("test-unit", [">= 2.4.3"])
 end
diff --git a/test/helper.rb b/test/helper.rb
index 02e9deb..ce0b383 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -1,5 +1,5 @@
 require 'rubygems'
-require 'test/unit'
+require 'test-unit'
 require 'uri'
 require 'http/cookie'