"controllers" should be a valid path name

2 files changed, 11 insertions, 1 deletions

diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 0a1f6afd77..67e7285dcd 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -117,7 +117,7 @@ module ActionDispatch
               options[$1.to_sym] ||= /.+?/
             end
 
-            if path_without_format.match(':controller')
+            if path_pattern.names.map(&:to_sym).include?(:controller)
               raise ArgumentError, ":controller segment is not allowed within a namespace block" if scope[:module]
 
               # Add a default constraint for :controller path segments that matches namespaced
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 8249403a65..d6477e19bb 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -99,6 +99,16 @@ class TestRoutingMapper < ActionDispatch::IntegrationTest
     end
   end
 
+  def test_namespace_without_controller_segment
+    draw do
+      namespace :admin do
+        get 'hello/:controllers/:action'
+      end
+    end
+    get '/admin/hello/foo/new'
+    assert_equal 'foo', @request.params["controllers"]
+  end
+
   def test_session_singleton_resource
     draw do
       resource :session do