diff --git a/actionpack/lib/action_dispatch/http/headers.rb b/actionpack/lib/action_dispatch/http/headers.rb
index bc5410dc38..40053e521a 100644
--- a/actionpack/lib/action_dispatch/http/headers.rb
+++ b/actionpack/lib/action_dispatch/http/headers.rb
@@ -30,24 +30,27 @@ module ActionDispatch
       HTTP_HEADER = /\A[A-Za-z0-9-]+\z/
 
       include Enumerable
-      attr_reader :env
 
-      def initialize(env = {}) # :nodoc:
-        @env = env
+      def self.from_hash(hash)
+        new ActionDispatch::Request.new hash
+      end
+
+      def initialize(request) # :nodoc:
+        @req = request
       end
 
       # Returns the value for the given key mapped to @env.
       def [](key)
-        @env[env_name(key)]
+        env[env_name(key)]
       end
 
       # Sets the given value for the key mapped to @env.
       def []=(key, value)
-        @env[env_name(key)] = value
+        env[env_name(key)] = value
       end
 
       def key?(key)
-        @env.key? env_name(key)
+        env.key? env_name(key)
       end
       alias :include? :key?
 
@@ -59,17 +62,17 @@ module ActionDispatch
       # If the code block is provided, then it will be run and
       # its result returned.
       def fetch(key, *args, &block)
-        @env.fetch env_name(key), *args, &block
+        env.fetch env_name(key), *args, &block
       end
 
       def each(&block)
-        @env.each(&block)
+        env.each(&block)
       end
 
       # Returns a new Http::Headers instance containing the contents of
       # <tt>headers_or_env</tt> and the original instance.
       def merge(headers_or_env)
-        headers = Http::Headers.new(env.dup)
+        headers = Http::Headers.new(ActionDispatch::Request.new(env.dup))
         headers.merge!(headers_or_env)
         headers
       end
@@ -83,7 +86,10 @@ module ActionDispatch
         end
       end
 
+      def env; @req.env; end
+
       private
+
       # Converts a HTTP header name to an environment variable name if it is
       # not contained within the headers hash.
       def env_name(key)
diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index de28cd0998..1f480eec73 100644
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
@@ -170,7 +170,7 @@ module ActionDispatch
     #
     #   request.headers["Content-Type"] # => "text/plain"
     def headers
-      @headers ||= Http::Headers.new(@env)
+      @headers ||= Http::Headers.new(self)
     end
 
     # Returns a +String+ with the last requested path including their params.
diff --git a/actionpack/lib/action_dispatch/testing/integration.rb b/actionpack/lib/action_dispatch/testing/integration.rb
index 0cdc6d4e77..4dfd4f3f71 100644
--- a/actionpack/lib/action_dispatch/testing/integration.rb
+++ b/actionpack/lib/action_dispatch/testing/integration.rb
@@ -359,10 +359,10 @@ module ActionDispatch
 
           # this modifies the passed request_env directly
           if headers.present?
-            Http::Headers.new(request_env).merge!(headers)
+            Http::Headers.from_hash(request_env).merge!(headers)
           end
           if env.present?
-            Http::Headers.new(request_env).merge!(env)
+            Http::Headers.from_hash(request_env).merge!(env)
           end
 
           session = Rack::Test::Session.new(_mock_session)
diff --git a/actionpack/test/dispatch/header_test.rb b/actionpack/test/dispatch/header_test.rb
index 782c2cb11d..79600b654b 100644
--- a/actionpack/test/dispatch/header_test.rb
+++ b/actionpack/test/dispatch/header_test.rb
@@ -2,7 +2,7 @@ require "abstract_unit"
 
 class HeaderTest < ActiveSupport::TestCase
   def make_headers(hash)
-    ActionDispatch::Http::Headers.new hash
+    ActionDispatch::Http::Headers.new ActionDispatch::Request.new hash
   end
 
   setup do