diff --git a/include/osmocom/gsm/protocol/ipaccess.h b/include/osmocom/gsm/protocol/ipaccess.h
index f98ebd6..ba6cb3b 100644
--- a/include/osmocom/gsm/protocol/ipaccess.h
+++ b/include/osmocom/gsm/protocol/ipaccess.h
@@ -35,6 +35,7 @@
 	IPAC_PROTO_EXT_SMSC	= 0x03,
 	IPAC_PROTO_EXT_ORC	= 0x04,		/* OML Router Control */
 	IPAC_PROTO_EXT_GSUP	= 0x05,		/* GSUP GPRS extension */
+	IPAC_PROTO_EXT_OAP	= 0x06,		/* Osmocom Authn Protocol */
 };
 
 enum ipaccess_msgtype {