diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index d44465e547..660e864d2a 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -185,7 +185,7 @@ module Rails
         end
 
         all = (railties.all - order)
-        all.push(self)   unless all.include?(self)
+        all.push(self)   unless (all + order).include?(self)
         order.push(:all) unless order.include?(:all)
 
         index = order.index(:all)
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index 7a047ef93a..4437e2c8af 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -1098,6 +1098,10 @@ YAML
 
       get("/assets/bar.js")
       assert_equal "// App's bar js\n;", last_response.body.strip
+
+      # ensure that railties are not added twice
+      railties = Rails.application.ordered_railties.map(&:class)
+      assert_equal railties, railties.uniq
     end
 
     test "railties_order adds :all with lowest priority if not given" do