diff --git a/components/coap/libcoap/include/coap/address.h b/components/coap/libcoap/include/coap/address.h
index 85db2046..b45e81e6 100644
--- a/components/coap/libcoap/include/coap/address.h
+++ b/components/coap/libcoap/include/coap/address.h
@@ -62,7 +62,9 @@ typedef struct coap_address_t {
     struct sockaddr         sa;
     struct sockaddr_storage st;
     struct sockaddr_in      sin;
+#if COAP_IPV6
     struct sockaddr_in6     sin6;
+#endif
   } addr;
 } coap_address_t;
 
@@ -79,10 +81,12 @@ _coap_address_isany_impl(const coap_address_t *a) {
   switch (a->addr.sa.sa_family) {
   case AF_INET:
     return a->addr.sin.sin_addr.s_addr == INADDR_ANY;
+#if COAP_IPV6
   case AF_INET6:
     return memcmp(&in6addr_any,
                   &a->addr.sin6.sin6_addr,
                   sizeof(in6addr_any)) == 0;
+#endif
   default:
     ;
   }
diff --git a/components/coap/libcoap/src/address.c b/components/coap/libcoap/src/address.c
index b4db76f0..acb9ba3c 100644
--- a/components/coap/libcoap/src/address.c
+++ b/components/coap/libcoap/src/address.c
@@ -28,10 +28,12 @@ coap_address_equals(const coap_address_t *a, const coap_address_t *b) {
      a->addr.sin.sin_port == b->addr.sin.sin_port && 
      memcmp(&a->addr.sin.sin_addr, &b->addr.sin.sin_addr, 
 	    sizeof(struct in_addr)) == 0;
+#if COAP_IPV6
  case AF_INET6:
    return a->addr.sin6.sin6_port == b->addr.sin6.sin6_port && 
      memcmp(&a->addr.sin6.sin6_addr, &b->addr.sin6.sin6_addr, 
 	    sizeof(struct in6_addr)) == 0;
+#endif
  default: /* fall through and signal error */
    ;
  }
@@ -45,8 +47,10 @@ int coap_is_mcast(const coap_address_t *a) {
  switch (a->addr.sa.sa_family) {
  case AF_INET:
    return IN_MULTICAST(ntohl(a->addr.sin.sin_addr.s_addr));
+#if COAP_IPV6
  case  AF_INET6:
    return IN6_IS_ADDR_MULTICAST(&a->addr.sin6.sin6_addr);
+#endif
  default:  /* fall through and signal error */
    ;
   }
diff --git a/components/coap/libcoap/src/debug.c b/components/coap/libcoap/src/debug.c
index d68438b7..e1afda60 100644
--- a/components/coap/libcoap/src/debug.c
+++ b/components/coap/libcoap/src/debug.c
@@ -170,6 +170,7 @@ coap_print_addr(const struct coap_address_t *addr, unsigned char *buf, size_t le
     addrptr = &addr->addr.sin.sin_addr;
     port = ntohs(addr->addr.sin.sin_port);
     break;
+#if COAP_IPV6
   case AF_INET6:
     if (len < 7) /* do not proceed if buffer is even too short for [::]:0 */
       return 0;
@@ -180,6 +181,7 @@ coap_print_addr(const struct coap_address_t *addr, unsigned char *buf, size_t le
     port = ntohs(addr->addr.sin6.sin6_port);
 
     break;
+#endif
   default:
     memcpy(buf, "(unknown address type)", min(22, len));
     return min(22, len);
diff --git a/components/coap/libcoap/src/net.c b/components/coap/libcoap/src/net.c
index e08aaa43..7ebe48ad 100644
--- a/components/coap/libcoap/src/net.c
+++ b/components/coap/libcoap/src/net.c
@@ -508,12 +508,14 @@ coap_transaction_id(const coap_address_t *peer, const coap_pdu_t *pdu,
     coap_hash((const unsigned char *)&peer->addr.sin.sin_addr,
 	      sizeof(peer->addr.sin.sin_addr), h);
     break;
+#if COAP_IPV6
   case AF_INET6:
     coap_hash((const unsigned char *)&peer->addr.sin6.sin6_port,
 	      sizeof(peer->addr.sin6.sin6_port), h);
     coap_hash((const unsigned char *)&peer->addr.sin6.sin6_addr,
 	      sizeof(peer->addr.sin6.sin6_addr), h);
     break;
+#endif
   default:
     return;
   }
diff --git a/components/coap/port/include/coap_config_posix.h b/components/coap/port/include/coap_config_posix.h
index a77e97f0..a925b8d2 100644
--- a/components/coap/port/include/coap_config_posix.h
+++ b/components/coap/port/include/coap_config_posix.h
@@ -36,6 +36,8 @@
 #define CUSTOM_COAP_NETWORK_SEND
 #define CUSTOM_COAP_NETWORK_READ
 
+#define COAP_IPV6 LWIP_IPV6
+
 #endif
 
 #endif /* COAP_CONFIG_POSIX_H_ */