diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 0eca8b58bfa8d6abadb7c66962daf70601b419b6..961441e355b37d06b003cbea245c178b21f4efc9 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -406,6 +406,8 @@ namespace __format
       _WidthPrec _M_width_kind : 2;
       _WidthPrec _M_prec_kind : 2;
       _Pres_type _M_type : 4;
+      unsigned   _M_reserved : 1;
+      unsigned   _M_reserved2 : 16;
       unsigned short _M_width;
       unsigned short _M_prec;
       char32_t _M_fill = ' ';