Also happens with gcc-snapshot, so this is definitely an upstream bug. g++ (Debian 20201127-1) 11.0.0 20201127 (experimental) [master revision 3493b0c3281:5c47353bc97:5e9f814d754be790aec5b69a95699a8af2654058] Reported upstream as: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98043 Looks like a very similar (but not identical) bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97634 Cheers, Ben