diff --git a/ChangeLog b/ChangeLog
index 0064f5b1..7e11bc5e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -20779,3 +20779,5 @@
 	* Fixed a bug in rdimport(1) that caused the cart title
 	uniqueness check to be applied to the incorrect string when
 	the '--set-string-title=' switch was used.
+2021-07-29 Fred Gleason <fredg@paravelsystems.com>
+	* Added a 'special use' warning to 'README'.
diff --git a/README b/README
index 46275ff7..8c82e954 100644
--- a/README
+++ b/README
@@ -3,6 +3,13 @@ This is the README file for the Rivendell package.
 This software comes with ABSOLUTELY NO WARRANTY. See the file COPYING for
 details.
 
+This is a special version of Rivendell, one that cosnsists of v3.x code
+with schema support for v4.x. It is intended for use in situations where
+it is desired to test v4.x instances as part of a larger v3.x system.
+
+UNLESS YOU UNDERSTAND EXACTLY WHAT YOU DOING, YOU DO NOT WANT TO USE
+THIS VERSION!
+
 Welcome to this release of the Rivendell Project. Rivendell aims
 to be a robust, functionally complete digital audio system for use in 
 professional radio broadcast environments.