Can't build top of tree

Running an ancient NetBSD and chrooting into a jail built from current less than a week ago. Running:

cvs update -Pd && ./build.sh -U -u -o -O BUILD_OBJ -T BUILD_TOOL release

Within the hour and I get the following error:

dependall ===> lib/libcurses/PSD.doc
# compile libcurses/refresh.o
/usr/src/BUILD_TOOL/bin/i486--netbsdelf-gcc -O2 -std=gnu99 -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare -Wsystem-headers -Wno-traditional -Wa,--fatal-warnings -Wreturn-type -Wswitch -Wshadow -Werror -fPIE --sysroot=/usr/src/BUILD_OBJ/destdir.i386 -I/usr/src/lib/libcurses -I/usr/src/lib/libterminfo -DHAVE_WCHAR -c refresh.c -o refresh.o
refresh.c: In function 'makech':
refresh.c:988:5: error: null argument where non-null required (argument 1) [-Werror=nonnull]
if (((clsp - nlsp >= strlen(clr_eol) &&
^
cc1: all warnings being treated as errors

Is this just the risk of building ToT?

Regards,

Paul N.