2 files changed, 4 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index f44c10f533..6529cf6f31 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -13,6 +13,8 @@ module ActionDispatch
           end
         end
 
+        attr_reader :app
+
         def initialize(app, constraints, request)
           @app, @constraints, @request = app, constraints, request
         end
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 24f9981f4b..01a068a9f2 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -512,6 +512,8 @@ module ActionDispatch
           end
 
           dispatcher = route.app
+          dispatcher = dispatcher.app while dispatcher.is_a?(Mapper::Constraints)
+
           if dispatcher.is_a?(Dispatcher) && dispatcher.controller(params, false)
             dispatcher.prepare_params!(params)
             return params