diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 045299281cf5604d682277057500c101f2ce623b..2311afc6c19129b9c907f3cdc7d2c4d5fd504318 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -491,9 +491,7 @@ def define_generate_prefix(app, name)
                 prefix_options = options.slice(*_route.segment_keys)
                 # we must actually delete prefix segment keys to avoid passing them to next url_for
                 _route.segment_keys.each { |k| options.delete(k) }
-                prefix = _routes.url_helpers.send("#{name}_path", prefix_options)
-                prefix = '' if prefix == '/'
-                prefix
+                _routes.url_helpers.send("#{name}_path", prefix_options)
               end
             end
           end
diff --git a/actionpack/test/dispatch/prefix_generation_test.rb b/actionpack/test/dispatch/prefix_generation_test.rb
index cfbf970a37725501f75c9c649a43cc420d4fa6e9..113608ecf4dd679aaaf6174326dbc9b38f9a7144 100644
--- a/actionpack/test/dispatch/prefix_generation_test.rb
+++ b/actionpack/test/dispatch/prefix_generation_test.rb
@@ -241,6 +241,11 @@ def setup
       assert_equal "/something/", app_object.root_path
     end
 
+    test "[OBJECT] generating application's route includes default_url_options[:trailing_slash]" do
+      RailsApplication.routes.default_url_options[:trailing_slash] = true
+      assert_equal "/awesome/blog/posts", engine_object.posts_path
+    end
+
     test "[OBJECT] generating engine's route with url_for" do
       path = engine_object.url_for(:controller => "inside_engine_generating",
                                    :action => "show",