The following test code: ``` std::byte v[3] = {std::byte(10), std::byte(20), std::byte(30)}; EXPECT_EQ(fmt::format(L"({})", fmt::join(v, v + 3, L", ")), L"(10, 20, 30)"); EXPECT_EQ(fmt::format(L"({:02X})", fmt::join(v, v + 3, L", ")), L"(0A, 14, 1E)"); ``` fails to compile at the 3rd line since 11.1. Adding: ``` namespace std { template <typename T, FMT_ENABLE_IF(std::is_same<T, std::byte>::value)> inline auto format_as(T b) -> unsigned char { return static_cast<unsigned char>(b); } } // namespace std ``` back instead of the member format_as thing seems to fix it.