The only change in my pull request was to remove a deprecated, unrelated header in uuid. This happened in the builds last night on develop: In file included from ./boost/config.hpp:61:0, from ./boost/chrono/config.hpp:15, from ./boost/chrono/detail/inlined/process_cpu_clocks.hpp:15, from libs\chrono\src\process_cpu_clocks.cpp:17: ./boost/type_traits/detail/common_arithmetic_type.hpp:209:27: error: duplicate 'const' BOOST_STATIC_CONSTANT(const int, selector = sizeof(select(cond() ? T() : U()))); ^ "x86_64-w64-mingw32-g++.exe" -std=c++03 -m64 -O0 -fno-inline -Wall -pedantic -g -Wextra -Wno-long-long -DBOOST_ALL_NO_LIB=1 -DBOOST_All_STATIC_LINK=1 -DBOOST_SYSTEM_STATIC_LINK=1 -I"." -c -o "bin.v2\libs\chrono\build\gcc-mingw64\debug\cxxstd-03-iso\link-static\process_cpu_clocks.o" "libs\chrono\src\process_cpu_clocks.cpp" ...failed gcc.compile.c++ bin.v2\libs\chrono\build\gcc-mingw64\debug\cxxstd-03-iso\link-static\process_cpu_clocks.o... Failed on cygwin and mingw builds: https://ci.appveyor.com/project/jeking3/uuid-gaamf/build/1.0.116-develop/job... Also failed in c++03 builds on unix: https://travis-ci.org/boostorg/uuid/jobs/376161574#L2158 gcc.compile.c++ ../../bin.v2/libs/chrono/build/gcc-7/release/cxxstd-03-iso/link-static/thread_clock.o In file included from ../../boost/config.hpp:61:0, from ../../boost/chrono/config.hpp:15, from ../../boost/chrono/detail/inlined/thread_clock.hpp:14, from ../../libs/chrono/src/thread_clock.cpp:18: ../../boost/type_traits/detail/common_arithmetic_type.hpp:209:27: error: duplicate ‘const’ BOOST_STATIC_CONSTANT(const int, selector = sizeof(select(cond() ? T() : U()))); ^ "g++-7" -std=c++03 -m64 -O3 -finline-functions -Wno-inline -Wall -pedantic -Wextra -Wno-long-long -DBOOST_ALL_NO_LIB=1 -DBOOST_All_STATIC_LINK=1 -DBOOST_SYSTEM_STATIC_LINK=1 -DNDEBUG -I"../.." -c -o "../../bin.v2/libs/chrono/build/gcc-7/release/cxxstd-03-iso/link-static/thread_clock.o" "../../libs/chrono/src/thread_clock.cpp" ...failed gcc.compile.c++ ../../bin.v2/libs/chrono/build/gcc-7/release/cxxstd-03-iso/link-static/thread_clock.o... Thanks, Jim