diff --git a/actionpack/lib/action_dispatch/testing/integration.rb b/actionpack/lib/action_dispatch/testing/integration.rb
index 9f7877fa46..2c4a3a356d 100644
--- a/actionpack/lib/action_dispatch/testing/integration.rb
+++ b/actionpack/lib/action_dispatch/testing/integration.rb
@@ -486,7 +486,7 @@ module ActionDispatch
     def self.app
       # DEPRECATE Rails application fallback
       # This should be set by the initializer
-      @@app || (defined?(Rails.application) && Rails.application) || nil
+      @@app || (defined?(Rails.application) && Rails.application.new) || nil
     end
 
     def self.app=(app)