diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 8a1c5698983c..6707f70024f2 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -578,6 +578,8 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 	if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 		unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
 
+		memset(&opts->ext_copy, 0, sizeof(opts->ext_copy));
+
 		if (mpext) {
 			if (opts->csum_reqd)
 				map_size += TCPOLEN_MPTCP_DSS_CHECKSUM;