https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117410
--- Comment #5 from Artyom Kolpakov <ddvamp007 at gmail dot com> --- Here is a slightly different example: template <int = 0> void foo(int = 0) {} template <int = 0> void foo(...) requires true {} int main() { foo(); } The current standard contains ambiguity regarding ellipsis. I suggested opening a new core issue (https://cplusplus.github.io/CWG/issues/2949.html) that can be tracked for this "bug".