diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index b3cb1248..8118298e 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -453,7 +453,7 @@ tcp_listen_input(struct tcp_pcb_listen *pcb)
     npcb->accept = pcb->accept;
 #endif /* LWIP_CALLBACK_API */
     /* inherit socket options */
-    npcb->so_options = pcb->so_options & (SOF_DEBUG|SOF_DONTROUTE|SOF_KEEPALIVE|SOF_OOBINLINE|SOF_LINGER);
+    npcb->so_options = pcb->so_options & SOF_INHERITED;
     /* Register the new PCB so that we can begin receiving segments
        for it. */
     TCP_REG(&tcp_active_pcbs, npcb);
diff --git a/src/include/ipv4/lwip/ip.h b/src/include/ipv4/lwip/ip.h
index ab8d214c..c908925f 100644
--- a/src/include/ipv4/lwip/ip.h
+++ b/src/include/ipv4/lwip/ip.h
@@ -100,10 +100,13 @@ struct ip_pcb {
 #define SOF_KEEPALIVE   (u16_t)0x0008U    /* keep connections alive */
 #define SOF_DONTROUTE   (u16_t)0x0010U    /* just use interface addresses */
 #define SOF_BROADCAST   (u16_t)0x0020U    /* permit to send and to receive broadcast messages (see IP_SOF_BROADCAST option) */
-#define SOF_USELOOPBACK (u16_t)0x0040U    /* bypass hardware when possible */
+/*#define SOF_USELOOPBACK (u16_t)0x0040U     Unimplemented: bypass hardware when possible */
 #define SOF_LINGER      (u16_t)0x0080U    /* linger on close if data present */
 #define SOF_OOBINLINE   (u16_t)0x0100U    /* leave received OOB data in line */
-#define SOF_REUSEPORT   (u16_t)0x0200U    /* allow local address & port reuse */
+/*#define SOF_REUSEPORT   (u16_t)0x0200U     Unimplemented: allow local address & port reuse */
+
+/* These flags are inherited (e.g. from a listen-pcb to a connection-pcb): */
+#define SOF_INHERITED   (SOF_DEBUG|SOF_REUSEADDR|SOF_DONTROUTE|SOF_KEEPALIVE|SOF_OOBINLINE|SOF_LINGER)
 
 
 #ifdef PACK_STRUCT_USE_INCLUDES