Engine routes in Application Controller

I have a before_filter hook in my main app's application controller that does something like: (It doesn't just put a link in the flash, there is a message, but it isn't relevant to the question, it just accesses the route in the method)

class ApplicationController < ActionController::Base
  before_filter :set_link

  def set_link
    flash[:notice] = items_path
  end
end

This works fine for the app, however when I go into the controllers for an engine I made I get the exception

No route matches {:controller=>"items", :action=>"index"}

I understand that when in the engine, the routes helpers are for the engine unless prefixed with main_app

So changing the method in the application controller to

  def set_link
    flash[:notice] = main_app.items_path
  end

Gets rid of the exception but I really don't want to have to do that. Is there another solution to getting the engine to recognize the main_app routes?

EDIT:

This also happens if the application layout calls path helpers. So if the engine is designed to integrated into the main_app's layout then this issue will crop there up too.