diff --git a/UPGRADE.txt b/UPGRADE.txt
index 5efea3edbf..4cd72a26db 100644
--- a/UPGRADE.txt
+++ b/UPGRADE.txt
@@ -18,6 +18,14 @@
 ===
 ===========================================================
 
+From 1.6.0.X to 1.6.0.15:
+
+* There have been some changes to the IAX2 protocol to address the security
+  concerns documented in the security advisory AST-2009-006.  Please see the
+  IAX2 security document, doc/IAX2-security.pdf, for information regarding
+  backwards compatibility with versions of Asterisk that do not contain these
+  changes to IAX2.
+
 From 1.6.0.10 to 1.6.0.11:
 
 * Beginning with this release, Asterisk's internal methods of