diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 479a3bfa87aa..fa50c0a7ff54 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -839,8 +839,11 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 
 	opts->suboptions = 0;
 
+	/* Force later mptcp_write_options(), but do not use any actual
+	 * option space.
+	 */
 	if (unlikely(__mptcp_check_fallback(msk) && !mptcp_check_infinite_map(skb)))
-		return false;
+		return true;
 
 	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 		if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
@@ -1319,6 +1322,20 @@ update_wspace:
 	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
 }
 
+static void mptcp_track_rwin(struct tcp_sock *tp)
+{
+	const struct sock *ssk = (const struct sock *)tp;
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk;
+
+	if (!ssk)
+		return;
+
+	subflow = mptcp_subflow_ctx(ssk);
+	msk = mptcp_sk(subflow->conn);
+	WRITE_ONCE(msk->old_wspace, tp->rcv_wnd);
+}
+
 __sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
 {
 	struct csum_pseudo_header header;
@@ -1611,6 +1628,10 @@ mp_rst:
 				      opts->reset_transient,
 				      opts->reset_reason);
 		return;
+	} else if (unlikely(!opts->suboptions)) {
+		/* Fallback to TCP */
+		mptcp_track_rwin(tp);
+		return;
 	}
 
 	if (OPTION_MPTCP_PRIO & opts->suboptions) {