So I have been using boost for awhile. I compile boost the same way for all the versions and have been since 1.48. My platforms are CentOS 6 & 7 and Windows 10 vs2017. My code has compiled on all 3 platforms with Boost without a problem. My current version is 1.66 and I wanted to upgrade to 1.69. Under Windows, I build 1.69 with ZLIB & BZIP and my applications have no problems. I use zlib & bzip in the IOstreams library to read & write compressed files. So I built 1.69 under Linux the same way as I always have but I am now getting a linker error that I don't understand and I am stuck. The error starts with: API_utiltyFunctions.cpp:(.text+0x154): undefined reference to `boost::iostreams::detail::zlib_base::before(char const*&, char const*, char*&, char*)' API_utiltyFunctions.cpp:(.text+0x15b): undefined reference to `boost::iostreams::zlib::sync_flush' API_utiltyFunctions.cpp:(.text+0x165): undefined reference to `boost::iostreams::detail::zlib_base::xinflate(int)' API_utiltyFunctions.cpp:(.text+0x177): undefined reference to `boost::iostreams::detail::zlib_base::after(char const*&, char*&, bool)' API_utiltyFunctions.cpp:(.text+0x17e): undefined reference to `boost::iostreams::zlib_error::check(int)' API_utiltyFunctions.cpp:(.text+0x185): undefined reference to `boost::iostreams::zlib::stream_end' The boost portion of my linker line is: -L[ path to boost 1.69] \ -lboost_random-1_69 \ -lboost_program_options-1_69 \ -lboost_date_time-1_69 \ -lboost_chrono-1_69 \ -lboost_regex-1_69 \ -lboost_thread-1_69 \ -lboost_exception-1_69 \ -lboost_filesystem-1_69 \ -lboost_system-1_69 \ -lboost_iostreams-1_69 -lrt -lbz2 -lz -lm Any help would be appreciate. Weirdly if I revert back to boost 1.66, I don't have a problem. I also tested this compilation against boost 1.70 and I get the same problem. I do compile boost statically with shared runtime libraries and threads. Respectfully, Danny K