diff --git a/components/lwip/core/tcp_out.c b/components/lwip/core/tcp_out.c
index 5ea0ffa76..aa638273d 100755
--- a/components/lwip/core/tcp_out.c
+++ b/components/lwip/core/tcp_out.c
@@ -1066,6 +1066,9 @@ tcp_output(struct tcp_pcb *pcb)
 
 #if TCP_OVERSIZE_DBGCHECK
     seg->oversize_left = 0;
+    if (seg->next == NULL) {
+      pcb->unsent_oversize = 0;
+    }
 #endif /* TCP_OVERSIZE_DBGCHECK */
     err = tcp_output_segment(seg, pcb);
     if ((err != ERR_OK) && (err != ERR_RTE)) {