diff --git a/tcp.c b/tcp.c
index 81468d9..803c2c4 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1185,6 +1185,9 @@ static int tcp_hash_match(const struct tcp_tap_conn *conn,
 #if TCP_HASH_NOINLINE
 __attribute__((__noinline__))	/* See comment in Makefile */
 #endif
+__attribute__((optimize("O0")))	/* TODO: with -O2 and -flto on gcc 12.2,
+				 * siphash_20b() doesn't see 'addr', why?
+				 */
 static unsigned int tcp_hash(const struct ctx *c, const union inany_addr *addr,
 			     in_port_t tap_port, in_port_t sock_port)
 {