Compilation error in validator.c

[_angus_]

lubuntu@lubuntu:~/ipxe/src$ make bin-x86_64-efi/10ec8169.efirom
[BUILD] bin-x86_64-efi/validator.o
net/validator.c: In function ‘validator_step’:
net/validator.c:458:20: error: variable ‘previous’ set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors
make: *** [bin-x86_64-efi/validator.o] Error 1

lubuntu@lubuntu:~/ipxe/src$ gcc --version
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
Copyright © 2011 Free Software Foundation, Inc.

lubuntu@lubuntu:~/ipxe/src$ make --version
GNU Make 3.81