From c5d66fe5ff956e6ac2b48327e72bd7bbe02e63de Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Wed, 20 Apr 2016 16:46:44 +0700
Subject: [PATCH] check ACK entropy before further handling of the ACK frame

---
 session.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/session.go b/session.go
index 464fe9a0..4321ddbc 100644
--- a/session.go
+++ b/session.go
@@ -190,12 +190,12 @@ func (s *Session) handleAckFrame(r *bytes.Reader) error {
 	if !ok {
 		return errors.New("No entropy value saved for received ACK packet")
 	}
-	delete(s.EntropyHistory, frame.LargestObserved)
 
 	if byte(expectedEntropy) != frame.Entropy {
 		return errors.New("Incorrect entropy value in ACK package")
 	}
 
+	delete(s.EntropyHistory, frame.LargestObserved)
 	return nil
 }