Compile err - 2.4.18-pre4 - undefined reference to `unload_mpu401'

drivers/sound/sounddrivers.o: In function `unload_sbmpu':
drivers/sound/sounddrivers.o(.text+0xc0b3): undefined reference to unload_mpu401' drivers/sound/sounddrivers.o(__ksymtab+0x2d0): undefined reference to unload_mpu401'
make: *** [vmlinux] Error 1

This is 2.4.18-pre4, any quick fixes?

-d