Rails, Devise authentication, CSRF issue

I'm doing a singe-page application using Rails. When signing in and out Devise controllers are invoked using ajax. The problem I'm getting is that when I 1) sign in 2) sign out then signing in again doesn't work. I think it's related to CSRF token which gets reset when I sign out (though it shouldn't afaik) and since it's single page, the old CSRF token is being sent in xhr request thus resetting