See upstream https://github.com/gabime/spdlog/issues/1975 --- a/include/spdlog/common-inl.h 2021-06-21 17:15:26.695992698 -0600 +++ b/include/spdlog/common-inl.h 2021-06-21 17:15:52.205992496 -0600 @@ -60,7 +60,7 @@ SPDLOG_INLINE spdlog_ex::spdlog_ex(const std::string &msg, int last_errno) { memory_buf_t outbuf; - fmt::format_system_error(outbuf, last_errno, msg); + fmt::format_system_error(outbuf, last_errno, msg.c_str()); msg_ = fmt::to_string(outbuf); }