diff --git a/sim_sock.h b/sim_sock.h
index 326720c7..6cf43650 100644
--- a/sim_sock.h
+++ b/sim_sock.h
@@ -90,8 +90,10 @@ extern "C" {
 #endif
 #define WSAEACCES       EACCES
 #define WSAEINTR        EINTR
-#define INVALID_SOCKET  ((SOCKET)-1) 
-#define SOCKET_ERROR    -1
+#define INVALID_SOCKET  ((SOCKET)-1)
+#if !defined(SOCKET_ERROR)
+#define SOCKET_ERROR    (-1)
+#endif
 #endif
 
 #if defined (VMS)                                       /* VMS unique */
diff --git a/slirp_glue/config-host.h b/slirp_glue/config-host.h
index bff61560..9bb557ce 100644
--- a/slirp_glue/config-host.h
+++ b/slirp_glue/config-host.h
@@ -8,6 +8,7 @@
 #include <winsock2.h>
 #else
 typedef int SOCKET;
+#define SOCKET_ERROR (-1)
 #endif
 
 #ifndef  __cplusplus