diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index 2c2bb1c7143ef855a678d98d91ee65ed7f825312..f6721c617fc2d6458f0da8b1183906fd34aaae1c 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -407,6 +407,8 @@ def find(path)
       end
     end
 
+    self.isolated = false
+
     delegate :middleware, :root, :paths, to: :config
     delegate :engine_name, :isolated?, to: "self.class"