diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index 198085f6..a9ff802b 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -1308,6 +1308,12 @@ lwip_netconn_do_listen(struct api_msg_msg *msg)
               }
             }
           }
+        } else if (msg->conn->state == NETCONN_LISTEN) {
+          /* already listening, allow updating of the backlog */
+          msg->err = ERR_OK;
+#if TCP_LISTEN_BACKLOG
+          tcp_backlog_set(msg->conn->pcb.tcp, msg->msg.lb.backlog);
+#endif /* TCP_LISTEN_BACKLOG */
         }
       } else {
         msg->err = ERR_ARG;
diff --git a/src/core/tcp.c b/src/core/tcp.c
index 58315d74..46f29808 100644
--- a/src/core/tcp.c
+++ b/src/core/tcp.c
@@ -587,7 +587,7 @@ tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
 #endif /* LWIP_CALLBACK_API */
 #if TCP_LISTEN_BACKLOG
   lpcb->accepts_pending = 0;
-  lpcb->backlog = (backlog ? backlog : 1);
+  tcp_backlog_set(lpcb, backlog);
 #endif /* TCP_LISTEN_BACKLOG */
   TCP_REG(&tcp_listen_pcbs.pcbs, (struct tcp_pcb *)lpcb);
   return (struct tcp_pcb *)lpcb;
diff --git a/src/include/lwip/tcp.h b/src/include/lwip/tcp.h
index 1c7440f4..dddd0fbc 100644
--- a/src/include/lwip/tcp.h
+++ b/src/include/lwip/tcp.h
@@ -362,6 +362,9 @@ void             tcp_err     (struct tcp_pcb *pcb, tcp_err_fn err);
 #define          tcp_accepted(pcb) do { \
   LWIP_ASSERT("pcb->state == LISTEN (called for wrong pcb?)", pcb->state == LISTEN); \
   (((struct tcp_pcb_listen *)(pcb))->accepts_pending--); } while(0)
+#define          tcp_backlog_set(pcb, new_backlog) do { \
+  LWIP_ASSERT("pcb->state == LISTEN (called for wrong pcb?)", (pcb)->state == LISTEN); \
+  ((struct tcp_pcb_listen *)(pcb))->backlog = ((new_backlog) ? (new_backlog) : 1); } while(0)
 #else  /* TCP_LISTEN_BACKLOG */
 #define          tcp_accepted(pcb) LWIP_ASSERT("pcb->state == LISTEN (called for wrong pcb?)", \
                                                (pcb)->state == LISTEN)