question about code in lstrlib.c

["Todor Totev" <umbra.tenebris@...>]

Hello all,
in lstrlib.c in luaI_addquotedbinary()
the code reads:
	sprintf(str, "\\x%04x", (unsigned long)*s);
on line 700 & 733. I wander why the cast is to long
when the format specifier of sprintf is for integer.
Regards,
Todor