diff --git a/ports/win32/pcapif_helper.c b/ports/win32/pcapif_helper.c
index 59a13b9..de5147f 100644
--- a/ports/win32/pcapif_helper.c
+++ b/ports/win32/pcapif_helper.c
@@ -29,7 +29,7 @@ struct pcapifh_linkstate {
   PPACKET_OID_DATA ppacket_oid_data;
 };
 
-struct pcapifh_linkstate* pcapifh_linkstate_init(const char *adapter_name)
+struct pcapifh_linkstate* pcapifh_linkstate_init(char *adapter_name)
 {
   struct pcapifh_linkstate* state = (struct pcapifh_linkstate*)malloc(sizeof(struct pcapifh_linkstate));
   if (state != NULL) {
@@ -86,7 +86,7 @@ struct pcapifh_linkstate {
   u8_t empty;
 };
 
-struct pcapifh_linkstate* pcapifh_linkstate_init(const char *adapter_name)
+struct pcapifh_linkstate* pcapifh_linkstate_init(char *adapter_name)
 {
   LWIP_UNUSED_ARG(adapter_name);
   return NULL;
diff --git a/ports/win32/pcapif_helper.h b/ports/win32/pcapif_helper.h
index 2ebde22..da08854 100644
--- a/ports/win32/pcapif_helper.h
+++ b/ports/win32/pcapif_helper.h
@@ -13,7 +13,7 @@ enum pcapifh_link_event {
   PCAPIF_LINKEVENT_DOWN
 };
 
-struct pcapifh_linkstate* pcapifh_linkstate_init(const char *adapter_name);
+struct pcapifh_linkstate* pcapifh_linkstate_init(char *adapter_name);
 enum pcapifh_link_event pcapifh_linkstate_get(struct pcapifh_linkstate* state);
 void pcapifh_linkstate_close(struct pcapifh_linkstate* state);
 
diff --git a/ports/win32/sio.c b/ports/win32/sio.c
index 7164407..2f44aaf 100644
--- a/ports/win32/sio.c
+++ b/ports/win32/sio.c
@@ -35,9 +35,13 @@
 #include <stdio.h>
 #include <stdarg.h>
 
+#ifdef _MSC_VER
 #pragma warning (push, 3)
+#endif
 #include <windows.h>
+#ifdef _MSC_VER
 #pragma warning (pop)
+#endif
 #include "lwipcfg_msvc.h"
 
 /** When 1, use COM ports, when 0, use named pipes (for simulation). */
@@ -172,18 +176,18 @@ sio_fd_t sio_open(u8_t devnum)
 #if SIO_USE_COMPORT
     if(!sio_setup(fileHandle)) {
       CloseHandle(fileHandle);
-      LWIP_DEBUGF(SIO_DEBUG, ("sio_open(%lu): sio_setup failed. GetLastError() returns %d\n",
+      LWIP_DEBUGF(SIO_DEBUG, ("sio_open(%lu): sio_setup failed. GetLastError() returns %lu\n",
                   (DWORD)devnum, GetLastError()));
       return NULL;
     }
 #endif /* SIO_USE_COMPORT */
     LWIP_DEBUGF(SIO_DEBUG, ("sio_open: file \"%s\" successfully opened.\n", fileName));
-    printf("sio_open: file \"%s\" (%lu) successfully opened: 0x%08x\n", fileName, devnum, (u32_t)fileHandle);
+    printf("sio_open: file \"%s\" (%d) successfully opened: 0x%08x\n", fileName, devnum, (unsigned int)(size_t)fileHandle);
     return (sio_fd_t)(fileHandle);
   }
-  LWIP_DEBUGF(SIO_DEBUG, ("sio_open(%lu) failed. GetLastError() returns %d\n",
+  LWIP_DEBUGF(SIO_DEBUG, ("sio_open(%lu) failed. GetLastError() returns %lu\n",
               (DWORD)devnum, GetLastError()));
-  printf("sio_open(%lu) failed. GetLastError() returns %d\n",
+  printf("sio_open(%lu) failed. GetLastError() returns %lu\n",
               (DWORD)devnum, GetLastError());
   return NULL;
 }
diff --git a/ports/win32/test.c b/ports/win32/test.c
index 70d7ab8..2b4b883 100644
--- a/ports/win32/test.c
+++ b/ports/win32/test.c
@@ -158,7 +158,7 @@ struct netif slipif2;
 
 
 #if PPP_SUPPORT
-void
+static void
 pppLinkStatusCallback(ppp_pcb *pcb, int errCode, void *ctx)
 {
   struct netif *pppif = ppp_netif(pcb);