diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e48e28e..4f8a8a1 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1295,6 +1295,7 @@
 	struct sk_buff *skb, *nskb, *next;
 	int len;
 	int probe_size;
+	int size_needed;
 	unsigned int pif;
 	int copy;
 	int mss_now;
@@ -1313,6 +1314,7 @@
 	/* Very simple search strategy: just double the MSS. */
 	mss_now = tcp_current_mss(sk, 0);
 	probe_size = 2*tp->mss_cache;
+	size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
 	if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
 		/* TODO: set timer for probe_converge_event */
 		return -1;
@@ -1322,18 +1324,15 @@
 	len = 0;
 	if ((skb = tcp_send_head(sk)) == NULL)
 		return -1;
-	while ((len += skb->len) < probe_size && !tcp_skb_is_last(sk, skb))
+	while ((len += skb->len) < size_needed && !tcp_skb_is_last(sk, skb))
 		skb = tcp_write_queue_next(sk, skb);
-	if (len < probe_size)
+	if (len < size_needed)
 		return -1;
 
-	/* Receive window check. */
-	if (after(TCP_SKB_CB(skb)->seq + probe_size, tp->snd_una + tp->snd_wnd)) {
-		if (tp->snd_wnd < probe_size)
-			return -1;
-		else
-			return 0;
-	}
+	if (tp->snd_wnd < size_needed)
+		return -1;
+	if (after(tp->snd_nxt + size_needed, tp->snd_una + tp->snd_wnd))
+		return 0;
 
 	/* Do we need to wait to drain cwnd? */
 	pif = tcp_packets_in_flight(tp);