1 files changed, 7 insertions, 2 deletions
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index ef1bee106a..b437d7a17d 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -277,8 +277,13 @@ module ActionDispatch
         private
           def app_name(app)
             return unless app.respond_to?(:routes)
-            class_name = app.class.is_a?(Class) ? app.name : app.class.name
-            ActiveSupport::Inflector.underscore(class_name).gsub("/", "_")
+
+            if app.respond_to?(:railtie_name)
+              app.railtie_name
+            else
+              class_name = app.class.is_a?(Class) ? app.name : app.class.name
+              ActiveSupport::Inflector.underscore(class_name).gsub("/", "_")
+            end
           end
 
           def define_generate_prefix(app, name)