diff --git a/sys/netpfil/ipfw/nat64/nat64stl.c b/sys/netpfil/ipfw/nat64/nat64stl.c
index 968e74e5572..3a13ababbd6 100644
--- a/sys/netpfil/ipfw/nat64/nat64stl.c
+++ b/sys/netpfil/ipfw/nat64/nat64stl.c
@@ -69,7 +69,7 @@ nat64stl_log(struct pfloghdr *plog, struct mbuf *m, sa_family_t family,
 {
 	static uint32_t pktid = 0;
 
-	memset(plog, 0, sizeof(plog));
+	memset(plog, 0, sizeof(*plog));
 	plog->length = PFLOG_REAL_HDRLEN;
 	plog->af = family;
 	plog->action = PF_NAT;