diff --git a/include/re_sip.h b/include/re_sip.h
index 5e892721a..f9c171765 100644
--- a/include/re_sip.h
+++ b/include/re_sip.h
@@ -150,6 +150,7 @@ enum {
 
 
 /** SIP Via header */
+#define RE_RFC3261_BRANCH_ID "z9hG4bK"
 struct sip_via {
 	struct pl sentby;
 	struct sa addr;