diff --git a/Gemfile.lock b/Gemfile.lock
index 4d9f39c3e7c0f9d5fb5af328902fabb85b559c7b..289b915a58ae49f6f1e68153bfb9c4038f74bfed 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -27,7 +27,7 @@ GIT
 
 GIT
   remote: git://github.com/rack/rack.git
-  revision: c94e22401d4719b4d78378c7b63362cd692f9005
+  revision: fd20c3fa80128b19341ba8a0e0fae3bdc7c4c483
   specs:
     rack (2.0.0.alpha)
       json
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index d860e002173a66fa46c12f6ef779c77cf3947745..0987efc474bf616eb0a2eb802fd0d00abb970e5b 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -257,11 +257,11 @@ def body_parts
     end
 
     def set_cookie(key, value)
-      ::Rack::Utils.set_cookie_header!(header, key, value)
+      header[SET_COOKIE] = ::Rack::Utils.add_cookie_to_header(header[SET_COOKIE], key, value)
     end
 
     def delete_cookie(key, value={})
-      ::Rack::Utils.delete_cookie_header!(header, key, value)
+      header[SET_COOKIE] = ::Rack::Utils.add_remove_cookie_to_header(header[SET_COOKIE], key, value)
     end
 
     # The location header we'll be responding with.