diff --git a/lib/faraday/adapter.rb b/lib/faraday/adapter.rb
index eb42e47c..5b0c9814 100644
--- a/lib/faraday/adapter.rb
+++ b/lib/faraday/adapter.rb
@@ -30,5 +30,9 @@ module Faraday
         env[:body] = ''
       end
     end
+
+    def response_headers(env)
+      env[:response_headers] ||= Utils::Headers.new
+    end
   end
 end
diff --git a/lib/faraday/adapter/action_dispatch.rb b/lib/faraday/adapter/action_dispatch.rb
index 2863d497..13553f7b 100644
--- a/lib/faraday/adapter/action_dispatch.rb
+++ b/lib/faraday/adapter/action_dispatch.rb
@@ -22,7 +22,7 @@ module Faraday
         @session.__send__(env[:method], env[:url].request_uri, env[:body], env[:request_headers])
         resp = @session.response
         env.update :status => resp.status, :body => resp.body
-        env[:response_headers].update resp.headers
+        response_headers(env).update resp.headers
         @app.call env
       end
     end
diff --git a/lib/faraday/adapter/em_synchrony.rb b/lib/faraday/adapter/em_synchrony.rb
index 3e2d5172..81ef4e50 100644
--- a/lib/faraday/adapter/em_synchrony.rb
+++ b/lib/faraday/adapter/em_synchrony.rb
@@ -8,20 +8,6 @@ module Faraday
         self.load_error = e
       end
 
-      class Header
-        include Net::HTTPHeader
-        def initialize response
-          @header = {}
-          response.response_header.each do |key, value|
-            case key
-            when "CONTENT_TYPE"; self.content_type = value
-            when "CONTENT_LENGTH"; self.content_length = value
-            else; self[key] = value
-            end
-          end
-        end
-      end
-
       def call(env)
         super
         request = EventMachine::HttpRequest.new(URI::parse(env[:url].to_s))
@@ -67,9 +53,10 @@ module Faraday
           client = block.call
         end
 
-        env.update(:status           => client.response_header.http_status.to_i,
-                   :response_headers => Header.new(client),
-                   :body             => client.response)
+        client.response_header.each do |name, value|
+          response_headers(env)[name.to_sym] = value
+        end
+        env.update :status => client.response_header.status, :body => client.response
 
         @app.call env
       rescue Errno::ECONNREFUSED
diff --git a/lib/faraday/adapter/excon.rb b/lib/faraday/adapter/excon.rb
index 9ed5f924..09f95440 100644
--- a/lib/faraday/adapter/excon.rb
+++ b/lib/faraday/adapter/excon.rb
@@ -22,7 +22,7 @@ module Faraday
           :body    => env[:body]
 
         env.update :status => resp.status.to_i, :body => resp.body
-        env[:response_headers].update resp.headers
+        response_headers(env).update resp.headers
 
         @app.call env
       rescue ::Excon::Errors::SocketError
diff --git a/lib/faraday/adapter/net_http.rb b/lib/faraday/adapter/net_http.rb
index d1619b2a..da8ca837 100644
--- a/lib/faraday/adapter/net_http.rb
+++ b/lib/faraday/adapter/net_http.rb
@@ -54,7 +54,7 @@ module Faraday
         end
 
         http_response.each_header do |key, value|
-          env[:response_headers][key] = value
+          response_headers(env)[key] = value
         end
         env.update :status => http_response.code.to_i, :body => http_response.body
 
diff --git a/lib/faraday/adapter/patron.rb b/lib/faraday/adapter/patron.rb
index 900b20d5..ff380533 100644
--- a/lib/faraday/adapter/patron.rb
+++ b/lib/faraday/adapter/patron.rb
@@ -26,7 +26,7 @@ module Faraday
         end
 
         env.update :status => response.status, :body => response.body
-        env[:response_headers].update response.headers
+        response_headers(env).update response.headers
 
         @app.call env
       end
diff --git a/lib/faraday/adapter/test.rb b/lib/faraday/adapter/test.rb
index 55258b15..d0be73a1 100644
--- a/lib/faraday/adapter/test.rb
+++ b/lib/faraday/adapter/test.rb
@@ -11,7 +11,7 @@ module Faraday
     # resp = test.get '/nigiri/sake.json'
     # resp.body # => 'hi world'
     #
-    class Test < Middleware
+    class Test < Faraday::Adapter
       attr_accessor :stubs
 
       def self.loaded?() false end
@@ -105,14 +105,13 @@ module Faraday
       end
 
       def call(env)
+        super
         normalized_path = Faraday::Utils.normalize_path(env[:url])
 
         if stub = stubs.match(env[:method], normalized_path, env[:body])
           status, headers, body = stub.block.call(env)
-          env.update \
-            :status           => status,
-            :response_headers => headers,
-            :body             => body
+          env.update :status => status, :body => body
+          response_headers(env).update headers
         else
           raise "no stubbed request for #{env[:method]} #{normalized_path} #{env[:body]}"
         end
diff --git a/lib/faraday/adapter/typhoeus.rb b/lib/faraday/adapter/typhoeus.rb
index 00a7dbf7..021e1602 100644
--- a/lib/faraday/adapter/typhoeus.rb
+++ b/lib/faraday/adapter/typhoeus.rb
@@ -32,7 +32,7 @@ module Faraday
         is_parallel = !!env[:parallel_manager]
         req.on_complete do |resp|
           env.update :status => resp.code, :body => resp.body
-          env[:response_headers].parse resp.headers
+          response_headers(env).parse resp.headers
           env[:response].finish(env) if is_parallel
         end
 
diff --git a/lib/faraday/request.rb b/lib/faraday/request.rb
index 6d363fdf..ee4b40da 100644
--- a/lib/faraday/request.rb
+++ b/lib/faraday/request.rb
@@ -73,7 +73,6 @@ module Faraday
         :body             => body,
         :url              => connection.build_url(path, env_params),
         :request_headers  => env_headers,
-        :response_headers => Utils::Headers.new,
         :parallel_manager => connection.parallel_manager,
         :request          => connection.options.merge(:proxy => connection.proxy),
         :ssl              => connection.ssl}
diff --git a/lib/faraday/utils.rb b/lib/faraday/utils.rb
index 08c8642f..02b2f3c6 100644
--- a/lib/faraday/utils.rb
+++ b/lib/faraday/utils.rb
@@ -23,6 +23,8 @@ module Faraday
       end
 
       def []=(k, v)
+        # join multiple values with a comma
+        v = v.to_ary.join(', ') if v.respond_to? :to_ary
         super(KeyMap[k], v)
       end
       
@@ -33,7 +35,12 @@ module Faraday
         header_string.split(/\r\n/).
           tap  { |a| a.shift if a.first.index('HTTP/') == 0 }. # drop the HTTP status line
           map  { |h| h.split(/:\s+/, 2) }.reject { |(k, v)| k.nil? }. # split key and value, ignore blank lines
-          each { |(k, v)| self[k] = v }
+          each { |key, value|
+            # join multiple values with a comma
+            if self[key] then self[key] << ', ' << value
+            else self[key] = value
+            end
+          }
       end
     end
 
diff --git a/test/adapters/live_test.rb b/test/adapters/live_test.rb
index 37dc023d..e9b740b2 100644
--- a/test/adapters/live_test.rb
+++ b/test/adapters/live_test.rb
@@ -31,6 +31,14 @@ else
           assert_match /text\/html/, response.headers['content-type'], 'lowercase fail'
         end
 
+        # https://github.com/geemus/excon/issues/10
+        unless %[Faraday::Adapter::Excon] == adapter.to_s
+          define_method "test_#{adapter}_GET_handles_headers_with_multiple_values" do
+            response = create_connection(adapter).get('multi')
+            assert_equal 'one, two', response.headers['set-cookie']
+          end
+        end
+
         define_method "test_#{adapter}_POST_send_url_encoded_params" do
           resp = create_connection(adapter).post do |req|
             req.url 'echo_name'
diff --git a/test/env_test.rb b/test/env_test.rb
index 80976b34..5bd8ecd2 100644
--- a/test/env_test.rb
+++ b/test/env_test.rb
@@ -29,12 +29,6 @@ class EnvTest < Faraday::TestCase
     assert_equal 'Faraday', headers['server']
   end
 
-  def test_response_headers_case_insensitive
-    headers = @env[:response_headers]
-    headers['Content-Type'] = 'application/json'
-    assert_equal 'application/json', headers['content-type']
-  end
-
   def test_request_create_stores_body
     assert_equal @input[:body], @env[:body]
   end
diff --git a/test/live_server.rb b/test/live_server.rb
index 2987130e..7afdb0dc 100644
--- a/test/live_server.rb
+++ b/test/live_server.rb
@@ -6,6 +6,7 @@ get '/hello_world' do
 end
 
 get '/json' do
+  content_type 'application/json'
   "[1,2,3]"
 end
 
@@ -19,26 +20,22 @@ post '/file' do
   end
 end
 
-post '/hello' do
-  "hello #{params[:name]}"
+%w[get post].each do |method|
+  send(method, '/hello') do
+    "hello #{params[:name]}"
+  end
 end
 
-get '/hello' do
-  "hello #{params[:name]}"
-end
-
-post '/echo_name' do
-  params[:name].inspect
-end
-
-put '/echo_name' do
-  params[:name].inspect
+%w[post put].each do |method|
+  send(method, '/echo_name') do
+    params[:name].inspect
+  end
 end
 
 delete '/delete_with_json' do
   %/{"deleted":true}/
 end
 
-delete '/delete_with_params' do
-  params[:deleted]
+get '/multi' do
+  [200, { 'Set-Cookie' => %w[ one two ] }, '']
 end