diff --git a/mozilla/include/xp_sock.h b/mozilla/include/xp_sock.h
index cc2a0d0a10b..be032bd437a 100644
--- a/mozilla/include/xp_sock.h
+++ b/mozilla/include/xp_sock.h
@@ -82,7 +82,9 @@ extern int dupsocket(int foo); /* always fails */
 #define BOOLEAN char
 #endif /* XP_WIN */
 
+#ifndef SOCKET_ERRNO
 #define SOCKET_ERRNO    XP_GetError()
+#endif
 
 /************************************************************************/