https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114685
--- Comment #4 from m.cencora at gmail dot com --- I've stumbled upon a related error when trying to export std::vector after inclusion of <format> in GMF: module; namespace std { class vector; namespace __format { using std::vector; } } export module std; export namespace std { #ifdef WORKAROUND namespace __format {} #endif using std::vector; }