diff --git a/bgpd/bgpd.h b/bgpd/bgpd.h
index 0b3d449..eb63895 100644
--- a/bgpd/bgpd.h
+++ b/bgpd/bgpd.h
@@ -648,6 +648,7 @@
 #define BGP_ATTR_AS4_PATH                       17
 #define BGP_ATTR_AS4_AGGREGATOR                 18
 #define BGP_ATTR_AS_PATHLIMIT                   21
+#define BGP_ATTR_ENCAP                          23
 
 /* BGP update origin.  */
 #define BGP_ORIGIN_IGP                           0