diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2602f1386160..c38506c5ea05 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1316,7 +1316,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 			goto alloc_skb;
 		}
 
-		must_collapse = (info->size_goal - skb->len > 0) &&
+		must_collapse = (info->size_goal > skb->len) &&
 				(skb_shinfo(skb)->nr_frags < sysctl_max_skb_frags);
 		if (must_collapse) {
 			size_bias = skb->len;
@@ -1325,7 +1325,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 	}
 
 alloc_skb:
-	if (!must_collapse && !ssk->sk_tx_skb_cache &&
+	if (!must_collapse &&
 	    !mptcp_alloc_tx_skb(sk, ssk, info->data_lock_held))
 		return 0;
 
@@ -1363,6 +1363,10 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 	}
 
 	mpext = skb_ext_find(tail, SKB_EXT_MPTCP);
+	if (!mpext)
+		pr_warn("must_collapse=%d old skb=%p:%d avail_size=%d:%d state=%d",
+			must_collapse, skb, skb ? skb->len:0, info->size_goal, avail_size,
+			ssk->sk_state);
 	if (WARN_ON_ONCE(!mpext)) {
 		/* should never reach here, stream corrupted */
 		return -EINVAL;