1 files changed, 3 insertions, 3 deletions
diff --git a/actionpack/lib/action_dispatch/http/headers.rb b/actionpack/lib/action_dispatch/http/headers.rb
index 1e43104f0a..505d5560b1 100644
--- a/actionpack/lib/action_dispatch/http/headers.rb
+++ b/actionpack/lib/action_dispatch/http/headers.rb
@@ -3,9 +3,10 @@ require 'active_support/memoizable'
 module ActionDispatch
   module Http
     class Headers < ::Hash
-      extend ActiveSupport::Memoizable
+      @@env_cache = Hash.new { |h,k| h[k] = "HTTP_#{k.upcase.gsub(/-/, '_')}" }
 
       def initialize(*args)
+
         if args.size == 1 && args[0].is_a?(Hash)
           super()
           update(args[0])
@@ -25,9 +26,8 @@ module ActionDispatch
       private
         # Converts a HTTP header name to an environment variable name.
         def env_name(header_name)
-          "HTTP_#{header_name.upcase.gsub(/-/, '_')}"
+          @@env_cache[header_name]
         end
-        memoize :env_name
     end
   end
 end