diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c
index eb81c380da1b..6e6b46cb1db9 100644
--- a/net/netfilter/xt_TCPMSS.c
+++ b/net/netfilter/xt_TCPMSS.c
@@ -148,16 +148,21 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 static u_int32_t tcpmss_reverse_mtu(const struct sk_buff *skb,
 				    unsigned int family)
 {
-	struct flowi fl = {};
+	struct flowi fl;
 	const struct nf_afinfo *ai;
 	struct rtable *rt = NULL;
 	u_int32_t mtu     = ~0U;
 
-	if (family == PF_INET)
-		fl.fl4_dst = ip_hdr(skb)->saddr;
-	else
-		fl.fl6_dst = ipv6_hdr(skb)->saddr;
+	if (family == PF_INET) {
+		struct flowi4 *fl4 = &fl.u.ip4;
+		memset(fl4, 0, sizeof(*fl4));
+		fl4->daddr = ip_hdr(skb)->saddr;
+	} else {
+		struct flowi6 *fl6 = &fl.u.ip6;
 
+		memset(fl6, 0, sizeof(*fl6));
+		ipv6_addr_copy(&fl6->daddr, &ipv6_hdr(skb)->saddr);
+	}
 	rcu_read_lock();
 	ai = nf_get_afinfo(family);
 	if (ai != NULL)