diff --git a/include/netinet/tcp.h b/include/netinet/tcp.h
index 2eac793eddf0efcda5b3b963a1c9709a1de7f39f..c7a86480d301a3dc864994ef2d75bd276bdff007 100644
--- a/include/netinet/tcp.h
+++ b/include/netinet/tcp.h
@@ -76,6 +76,7 @@ enum {
 	TCP_NLA_BYTES_RETRANS,
 	TCP_NLA_DSACK_DUPS,
 	TCP_NLA_REORD_SEEN,
+	TCP_NLA_SRTT,
 };
 
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)