diff --git a/app/assets/javascripts/application.js b/app/assets/javascripts/application.js
index 38059333c1e0..138e35d3b0bb 100644
--- a/app/assets/javascripts/application.js
+++ b/app/assets/javascripts/application.js
@@ -574,8 +574,10 @@ jQuery(document).ready(function($) {
       var header = 'X-CSRF-Token',
       token = csrf_meta_tag.attr('content');
 
-      request.setRequestHeader[header] = token;
+      request.setRequestHeader(header, token);
     }
+
+    request.setRequestHeader('X-Authentication-Scheme', "Session");
   });
   // ajaxStop gets called when ALL Requests finish, so we won't need a counter as in PT
   $(document).ajaxStop(function () {
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index d28ab13110fb..56e49671bbce 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -186,7 +186,17 @@ def require_login
       end
       respond_to do |format|
         format.any(:html, :atom) { redirect_to signin_path(:back_url => url) }
-        format.any(:xml, :js, :json)  { head :unauthorized, "Reason" => "login needed" }
+
+        authentication_scheme = if request.headers["X-Authentication-Scheme"] == "Session"
+          'Session'
+        else
+          'Basic'
+        end
+        format.any(:xml, :js, :json)  {
+          head :unauthorized,
+          "Reason" => "login needed",
+          'WWW-Authenticate' => authentication_scheme + ' realm="OpenProject API"' 
+        }
       end
       return false
     end
diff --git a/doc/CHANGELOG.md b/doc/CHANGELOG.md
index f4d8f6d88f41..e5c4a1398a55 100644
--- a/doc/CHANGELOG.md
+++ b/doc/CHANGELOG.md
@@ -2,4 +2,4 @@
 
 * `#1209` Fix adding watcher to issue
 * `#1034` Create changelog and document format
-
+* `#1301` Ajax call when logged out should open a popup window
diff --git a/test/integration/api_test/http_accept_auth_test.rb b/test/integration/api_test/http_accept_auth_test.rb
new file mode 100644
index 000000000000..097a42407537
--- /dev/null
+++ b/test/integration/api_test/http_accept_auth_test.rb
@@ -0,0 +1,43 @@
+#-- encoding: UTF-8
+#-- copyright
+# OpenProject is a project management system.
+#
+# Copyright (C) 2012-2013 the OpenProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# See doc/COPYRIGHT.rdoc for more details.
+#++
+
+require File.expand_path('../../../test_helper', __FILE__)
+
+class ApiTest::HttpAcceptAuthTest < ActionDispatch::IntegrationTest
+  fixtures :all
+
+  def setup
+    Setting.rest_api_enabled = '1'
+    Setting.login_required = '1'
+  end
+
+  def teardown
+    Setting.rest_api_enabled = '0'
+    Setting.login_required = '0'
+  end
+
+  # Using the NewsController because it's a simple API.
+  context "get /news" do
+    setup do
+      project = Project.find('onlinestore')
+      EnabledModule.create(:project => project, :name => 'news')
+    end
+
+    context "in :xml format" do
+      should_send_correct_authentication_scheme_when_header_authentication_scheme_is_session(:get, "/api/v1/projects/onlinestore/news.xml")
+    end
+
+    context "in :json format" do
+      should_send_correct_authentication_scheme_when_header_authentication_scheme_is_session(:get, "/api/v1/projects/onlinestore/news.json")
+    end
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 9c67c0da63de..25ebf60ccdd3 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -285,6 +285,43 @@ def self.should_allow_api_authentication(http_method, url, parameters={}, option
     should_allow_key_based_auth(http_method, url, parameters, options)
   end
 
+  # Test that a request allows the username and password for HTTP BASIC
+  #
+  # @param [Symbol] http_method the HTTP method for request (:get, :post, :put, :delete)
+  # @param [String] url the request url
+  # @param [optional, Hash] options additional options
+  # @option options [Symbol] :success_code Successful response code (:success)
+  # @option options [Symbol] :failure_code Failure response code (:unauthorized)
+  def self.should_send_correct_authentication_scheme_when_header_authentication_scheme_is_session(http_method, url, options = {}, parameters = {})
+    success_code = options[:success_code] || :success
+    failure_code = options[:failure_code] || :unauthorized
+
+    context "should not send www authenticate when header accept auth is session #{http_method} #{url}" do
+      context "without credentials" do
+        setup do
+          send(http_method, url, parameters, { "X-Authentication-Scheme" => "Session" })
+        end
+
+        should respond_with failure_code
+        should_respond_with_content_type_based_on_url(url)
+        should "include correct www_authenticate_header" do
+          # the 3.0.9 implementation of head leads to Www as the method capitalizes each
+          # word split by a hyphen.
+          # this is fixed in 3.1.0 http://apidock.com/rails/v3.1.0/ActionController/Head/head
+          # remove this switch once on 3.1.0
+          if ::Rails::VERSION::MAJOR == 3 && ::Rails::VERSION::MINOR == 0
+            assert @controller.response.headers.has_key?('Www-Authenticate')
+            assert_equal 'Session realm="OpenProject API"', @controller.response.headers['Www-Authenticate']
+          else
+            assert @controller.response.headers.has_key?('WWW-Authenticate')
+            assert_equal 'Session realm="OpenProject API"', @controller.response.headers['WWW-Authenticate']
+          end
+        end
+      end
+    end
+
+  end
+
   # Test that a request allows the username and password for HTTP BASIC
   #
   # @param [Symbol] http_method the HTTP method for request (:get, :post, :put, :delete)
@@ -333,6 +370,17 @@ def self.should_allow_http_basic_auth_with_username_and_password(http_method, ur
 
         should respond_with failure_code
         should_respond_with_content_type_based_on_url(url)
+        should "include_www_authenticate_header" do
+          # the 3.0.9 implementation of head leads to Www as the method capitalizes each
+          # word split by a hyphen.
+          # this is fixed in 3.1.0 http://apidock.com/rails/v3.1.0/ActionController/Head/head
+          # remove this switch once on 3.1.0
+          if ::Rails::VERSION::MAJOR == 3 && ::Rails::VERSION::MINOR == 0
+            assert @controller.response.headers.has_key?('Www-Authenticate')
+          else
+            assert @controller.response.headers.has_key?('WWW-Authenticate')
+          end
+        end
       end
     end