diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 8b46790fd2a45..2a25a8c4eaec9 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -208,6 +208,7 @@ def redirect(*args, &block)
             uri = URI.parse(path_proc.call(req.params))
             uri.scheme ||= req.scheme
             uri.host   ||= req.host
+            uri.port   ||= req.port unless req.port == 80
 
             headers = {
               'Location' => uri.to_s,
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 21bd7d5ac0103..a746c7e2edc5e 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -507,6 +507,18 @@ def test_redirect_with_complete_url
     end
   end
 
+  def test_redirect_with_port
+    previous_host, self.host = self.host, 'www.example.com:3000'
+    with_test_routes do
+      get '/account/login'
+      assert_equal 301, @response.status
+      assert_equal 'http://www.example.com:3000/login', @response.headers['Location']
+      assert_equal 'Moved Permanently', @response.body
+    end
+  ensure
+    self.host = previous_host
+  end
+
   private
     def with_test_routes
       real_routes, temp_routes = ActionController::Routing::Routes, Routes