diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index b819f2e613..f25e853e84 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,5 +1,10 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Copy literal route constraints to defaults so that url generation know about them.
+    The copied constraints are `:protocol`, `:subdomain`, `:domain`, `:host` and `:port`.
+
+    *Andrew White*
+
 *   `respond_to` and `respond_with` now raise ActionController::UnknownFormat instead
     of directly returning head 406. The exception is rescued and converted to 406
     in the exception handling middleware. *Steven Soroka*
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 2a7d540517..7a22b65c44 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/hash/except'
 require 'active_support/core_ext/hash/reverse_merge'
+require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/enumerable'
 require 'active_support/inflector'
@@ -100,6 +101,10 @@ module ActionDispatch
                 raise ArgumentError, "Regexp multiline option not allowed in routing requirements: #{requirement.inspect}"
               end
             end
+
+            if @options[:constraints].is_a?(Hash)
+              (@options[:defaults] ||= {}).reverse_merge!(defaults_from_constraints(@options[:constraints]))
+            end
           end
 
           # match "account/overview"
@@ -245,6 +250,11 @@ module ActionDispatch
           def default_action
             @options[:action] || @scope[:action]
           end
+
+          def defaults_from_constraints(constraints)
+            url_keys = [:protocol, :subdomain, :domain, :host, :port]
+            constraints.slice(*url_keys).select{ |k, v| v.is_a?(String) || v.is_a?(Fixnum) }
+          end
       end
 
       # Invokes Rack::Mount::Utils.normalize path and ensure that
@@ -641,6 +651,10 @@ module ActionDispatch
             block, options[:constraints] = options[:constraints], {}
           end
 
+          if options[:constraints].is_a?(Hash)
+            (options[:defaults] ||= {}).reverse_merge!(defaults_from_constraints(options[:constraints]))
+          end
+
           scope_options.each do |option|
             if value = options.delete(option)
               recover[option] = @scope[option]
@@ -849,6 +863,11 @@ module ActionDispatch
           def override_keys(child) #:nodoc:
             child.key?(:only) || child.key?(:except) ? [:only, :except] : []
           end
+
+          def defaults_from_constraints(constraints)
+            url_keys = [:protocol, :subdomain, :domain, :host, :port]
+            constraints.slice(*url_keys).select{ |k, v| v.is_a?(String) || v.is_a?(Fixnum) }
+          end
       end
 
       # Resource routing allows you to quickly declare all of the common routes
diff --git a/actionpack/test/dispatch/routing_assertions_test.rb b/actionpack/test/dispatch/routing_assertions_test.rb
index e953029456..517354ae58 100644
--- a/actionpack/test/dispatch/routing_assertions_test.rb
+++ b/actionpack/test/dispatch/routing_assertions_test.rb
@@ -47,7 +47,7 @@ class RoutingAssertionsTest < ActionController::TestCase
   def test_assert_recognizes_with_extras
     assert_recognizes({ :controller => 'articles', :action => 'index', :page => '1' }, '/articles', { :page => '1' })
   end
- 
+
   def test_assert_recognizes_with_method
     assert_recognizes({ :controller => 'articles', :action => 'create' }, { :path => '/articles', :method => :post })
     assert_recognizes({ :controller => 'articles', :action => 'update', :id => '1' }, { :path => '/articles/1', :method => :put })
@@ -57,7 +57,7 @@ class RoutingAssertionsTest < ActionController::TestCase
     assert_raise(ActionController::RoutingError) do
       assert_recognizes({ :controller => 'secure_articles', :action => 'index' }, 'http://test.host/secure/articles')
     end
-    assert_recognizes({ :controller => 'secure_articles', :action => 'index' }, 'https://test.host/secure/articles')
+    assert_recognizes({ :controller => 'secure_articles', :action => 'index', :protocol => 'https://' }, 'https://test.host/secure/articles')
   end
 
   def test_assert_recognizes_with_block_constraint
@@ -90,7 +90,7 @@ class RoutingAssertionsTest < ActionController::TestCase
     assert_raise(ActionController::RoutingError) do
       assert_routing('http://test.host/secure/articles', { :controller => 'secure_articles', :action => 'index' })
     end
-    assert_routing('https://test.host/secure/articles', { :controller => 'secure_articles', :action => 'index' })
+    assert_routing('https://test.host/secure/articles', { :controller => 'secure_articles', :action => 'index', :protocol => 'https://' })
   end
 
   def test_assert_routing_with_block_constraint
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 6f22cb3ea8..3cec816f1c 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -2606,3 +2606,45 @@ class TestNamedRouteUrlHelpers < ActionDispatch::IntegrationTest
     assert_raises(ActionController::RoutingError) { product_path(nil) }
   end
 end
+
+class TestUrlConstraints < ActionDispatch::IntegrationTest
+  Routes = ActionDispatch::Routing::RouteSet.new.tap do |app|
+    app.draw do
+      ok = lambda { |env| [200, { 'Content-Type' => 'text/plain' }, []] }
+
+      constraints :subdomain => 'admin' do
+        get '/' => ok, :as => :admin_root
+      end
+
+      scope :constraints => { :protocol => 'https://' } do
+        get '/' => ok, :as => :secure_root
+      end
+
+      get '/' => ok, :as => :alternate_root, :constraints => { :port => 8080 }
+    end
+  end
+
+  include Routes.url_helpers
+  def app; Routes end
+
+  test "constraints are copied to defaults when using constraints method" do
+    assert_equal 'http://admin.example.com/', admin_root_url
+
+    get 'http://admin.example.com/'
+    assert_response :success
+  end
+
+  test "constraints are copied to defaults when using scope constraints hash" do
+    assert_equal 'https://www.example.com/', secure_root_url
+
+    get 'https://www.example.com/'
+    assert_response :success
+  end
+
+  test "constraints are copied to defaults when using route constraints hash" do
+    assert_equal 'http://www.example.com:8080/', alternate_root_url
+
+    get 'http://www.example.com:8080/'
+    assert_response :success
+  end
+end