diff --git a/ports/unix/unixsim/lwipopts.h b/ports/unix/unixsim/lwipopts.h
index 68ce048..5921475 100644
--- a/ports/unix/unixsim/lwipopts.h
+++ b/ports/unix/unixsim/lwipopts.h
@@ -280,7 +280,7 @@ extern void sntp_set_system_time(u32_t sec);
 
 /* ---------- SLIP options ---------- */
 
-#define LWIP_HAVE_SLIPIF  1      /* Set > 0 for SLIP */
+#define LWIP_HAVE_SLIPIF  0      /* Set > 0 for SLIP */
 
 /* Maximum packet size that is received by this netif */
 #define SLIP_MAX_SIZE     1500
diff --git a/ports/unix/unixsim/simhost.c b/ports/unix/unixsim/simhost.c
index 58f1206..accaf83 100644
--- a/ports/unix/unixsim/simhost.c
+++ b/ports/unix/unixsim/simhost.c
@@ -474,7 +474,7 @@ init_netifs(void)
 
 #if LWIP_IPV4
   netif_add(&slipif, ip_2_ip4(&ipaddr_slip), ip_2_ip4(&netmask_slip), ip_2_ip4(&gw_slip),
-            (void*)&siodev_slip, slipif_init, tcpip_input);
+            LWIP_PTR_NUMERIC_CAST(void*, siodev_slip), slipif_init, tcpip_input);
 #else /* LWIP_IPV4 */
   netif_add(&slipif, (void*)&siodev_slip, slipif_init, tcpip_input);
 #endif /* LWIP_IPV4 */