diff -Naur SDL2_net-2.0.1/SDLnetsys.h SDL2_net-2.0.1.serenity/SDLnetsys.h
--- SDL2_net-2.0.1/SDLnetsys.h	2021-06-16 10:42:24.609750625 +0200
+++ SDL2_net-2.0.1.serenity/SDLnetsys.h	2016-01-03 08:57:09.000000000 +0100
@@ -46,6 +46,7 @@
 #include <iphlpapi.h>
 #else /* UNIX */
 #include <sys/types.h>
+#include <sys/select.h>
 #ifdef __FreeBSD__
 #include <sys/socket.h>
 #endif