https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103118
--- Comment #1 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> --- To work around this - Do not include `<chrono>`. - Explicitly import a module that exports its definitions when you need to use the chrono library. I use the headers above to compile a header unit, which I export from a module to work around the lack of a standard modules. Apparently, `<chrono>` is indirectly included, as using the chrono library works.