diff --git a/xen/include/public/io/sndif.h b/xen/include/public/io/sndif.h
index c5c1978406..667e610fda 100644
--- a/xen/include/public/io/sndif.h
+++ b/xen/include/public/io/sndif.h
@@ -36,6 +36,13 @@
 #include "ring.h"
 #include "../grant_table.h"
 
+/*
+ ******************************************************************************
+ *                           Protocol version
+ ******************************************************************************
+ */
+#define XENSND_PROTOCOL_VERSION         1
+
 /*
  ******************************************************************************
  *                  Feature and Parameter Negotiation