diff --git a/Quake/net_sys.h b/Quake/net_sys.h
index b7fee847..508edd20 100644
--- a/Quake/net_sys.h
+++ b/Quake/net_sys.h
@@ -142,7 +142,11 @@ typedef int	socklen_t;
 typedef SOCKET	sys_socket_t;
 
 #define	SOCKETERRNO	WSAGetLastError()
+/* the new MS SDKs define the following two,
+ * so we must undefine them before redefining. */
+#undef	EWOULDBLOCK
 #define	EWOULDBLOCK	WSAEWOULDBLOCK
+#undef	ECONNREFUSED
 #define	ECONNREFUSED	WSAECONNREFUSED
 /* must #include "wsaerror.h" for this : */
 #define	socketerror(x)	__WSAE_StrError((x))