crack-me cannot compile because "system" was not declared in the scope

[nitrocode]

I'm on linux and had to also include cstdlib to compile crack-me in the first tutorial

✗ g++ crack-me.cpp -o crack-me
crack-me.cpp: In function ‘void secret()’:
crack-me.cpp:17:23: error: ‘system’ was not declared in this scope
    system("uname -a\n");

Added and it compiles correctly with g++ 5.4.0

#include <cstdlib>

Maybe my g++ version is too old.