When compiling on a 32-bit system like Raspian on an RPi4, the compile dies: CC [M] fs/exfat/misc.o fs/exfat/misc.c: In function 'exfat_time_unix2fat': fs/exfat/misc.c:157:16: error: 'UNIX_SECS_2108' undeclared (first use in this function); did you mean 'UNIX_SECS_1980'? if (second >= UNIX_SECS_2108) { ^~~~~~~~~~~~~~ UNIX_SECS_1980 fs/exfat/misc.c:157:16: note: each undeclared identifier is reported only once for each function it appears in make[2]: *** [scripts/Makefile.build:266: fs/exfat/misc.o] Error 1 The problem is that the definition of UNIX_SECS_2108 is wrapped: +#if BITS_PER_LONG == 64 +#define UNIX_SECS_2108 4354819200L +#endif but the usage isn't.