2 files changed, 12 insertions, 2 deletions
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index b437d7a17d..900900ee24 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -274,6 +274,12 @@ module ActionDispatch
         end
         alias_method :default_url_options, :default_url_options=
 
+        def with_default_scope(scope, &block)
+          scope(scope) do
+            instance_exec(&block)
+          end
+        end
+
         private
           def app_name(app)
             return unless app.respond_to?(:routes)
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 0d83ca956b..107e44287d 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -199,7 +199,7 @@ module ActionDispatch
           end
       end
 
-      attr_accessor :set, :routes, :named_routes
+      attr_accessor :set, :routes, :named_routes, :default_scope
       attr_accessor :disable_clear_and_finalize, :resources_path_names
       attr_accessor :default_url_options, :request_class, :valid_conditions
 
@@ -230,7 +230,11 @@ module ActionDispatch
         if block.arity == 1
           mapper.instance_exec(DeprecatedMapper.new(self), &block)
         else
-          mapper.instance_exec(&block)
+          if default_scope
+            mapper.with_default_scope(default_scope, &block)
+          else
+            mapper.instance_exec(&block)
+          end
         end
 
         finalize! unless @disable_clear_and_finalize