diff --git a/include/fmt/core.h b/include/fmt/core.h
index 9a9b1a84..4ca9c3f8 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -291,6 +291,7 @@ struct monostate {
 #  define FMT_ENABLE_IF(...) fmt::enable_if_t<(__VA_ARGS__), int> = 0
 #endif
 
+// This is defined in core.h instead of format.h to avoid injecting in std.
 #ifdef __cpp_lib_byte
 inline auto format_as(std::byte b) -> unsigned char {
   return static_cast<unsigned char>(b);