Scala specs with Lift TestKit - example of doAroundExpectations not working

val post_session = post("session", "token" -> token)

"API2" should {
  "/session POST" in {  

    def withSession(a: => Any) = for(sess <- post_session) { a }
    doAroundExpectations(withSession(_))

    "Attempt to log in with a valid token should succeed with a 200 response" in {
      (sess.xml \ "session" \ "user" \ "id").text must be equalTo (theUser.id.toString)
      sess.code must be equalTo 200
    }
  }
}