Compilation failure on Centos and Gentoo

I don't have the exact build on when this started, but have seen it since at least build 1149

 g++ -DHAVE_CONFIG_H -I.. -I.. -ggdb3 -pthread -pipe -O3 -Werror -pedantic -Wall -Wextra -Wundef -Wshadow -fdiagnostics-show-option -fvisibility=hidden -Wformat -fno-strict-aliasing -Wno-strict-aliasing -Woverloaded-virtual -Wnon-virtual-dtor -Wctor-dtor-privacy -Wno-long-long -Wno-redundant-decls -std=gnu++98 -MT join.o -MD -MP -MF $depbase.Tpo -c -o join.o join.cc &&\
 mv -f $depbase.Tpo $depbase.Po
cc1plus: warnings being treated as errors
join.cc: In function 'void best_access_path(JOIN*, JoinTable*, Session*, table_map, uint32_t, double, double)':
join.cc:3295: warning: converting to non-pointer type 'uint32_t' from NULL
make[3]: *** [join.o] Error 1

Fails on these machines:
http://solace.inaugust.com/builders/gentoo8.32.1
http://solace.inaugust.com/builders/centos5.64.1.staging
http://solace.inaugust.com/builders/centos5.64.1-mt