--- a/actionpack/actionpack.gemspec
+++ b/actionpack/actionpack.gemspec
@@ -36,6 +36,7 @@
   s.add_dependency "activesupport", version
 
   s.add_dependency "rack", ">= 2.0.9"
+  s.add_dependency "rack-session", ">= 1.0.1"
   s.add_dependency "rack-test", ">= 0.6.3"
   s.add_dependency "rails-html-sanitizer", "~> 1.0", ">= 1.2.0"
   s.add_dependency "rails-dom-testing", "~> 2.0"