diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index dd88e1e5..1ee0e127 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -886,7 +886,8 @@ tcp_process(struct tcp_pcb *pcb)
   case FIN_WAIT_1:
     tcp_receive(pcb);
     if (recv_flags & TF_GOT_FIN) {
-      if ((flags & TCP_ACK) && (ackno == pcb->snd_nxt)) {
+      if ((flags & TCP_ACK) && (ackno == pcb->snd_nxt) &&
+          pcb->unsent == NULL) {
         LWIP_DEBUGF(TCP_DEBUG,
           ("TCP connection closed: FIN_WAIT_1 %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
         tcp_ack_now(pcb);
@@ -898,7 +899,8 @@ tcp_process(struct tcp_pcb *pcb)
         tcp_ack_now(pcb);
         pcb->state = CLOSING;
       }
-    } else if ((flags & TCP_ACK) && (ackno == pcb->snd_nxt)) {
+    } else if ((flags & TCP_ACK) && (ackno == pcb->snd_nxt) &&
+               pcb->unsent == NULL) {
       pcb->state = FIN_WAIT_2;
     }
     break;
@@ -915,7 +917,7 @@ tcp_process(struct tcp_pcb *pcb)
     break;
   case CLOSING:
     tcp_receive(pcb);
-    if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
+    if (flags & TCP_ACK && ackno == pcb->snd_nxt && pcb->unsent == NULL) {
       LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed: CLOSING %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
       tcp_pcb_purge(pcb);
       TCP_RMV_ACTIVE(pcb);
@@ -925,7 +927,7 @@ tcp_process(struct tcp_pcb *pcb)
     break;
   case LAST_ACK:
     tcp_receive(pcb);
-    if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
+    if (flags & TCP_ACK && ackno == pcb->snd_nxt && pcb->unsent == NULL) {
       LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed: LAST_ACK %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
       /* bugfix #21699: don't set pcb->state to CLOSED here or we risk leaking segments */
       recv_flags |= TF_CLOSED;