diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1436,14 +1436,6 @@
 #  define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
 #endif
 
-#if defined(_AIX) && !defined(_LIBCPP_COMPILER_GCC)
-#  define _LIBCPP_PACKED_BYTE_FOR_AIX _Pragma("pack(1)")
-#  define _LIBCPP_PACKED_BYTE_FOR_AIX_END _Pragma("pack(pop)")
-#else
-#  define _LIBCPP_PACKED_BYTE_FOR_AIX      /* empty */
-#  define _LIBCPP_PACKED_BYTE_FOR_AIX_END  /* empty */
-#endif
-
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG
diff --git a/libcxx/include/__format/parser_std_format_spec.h b/libcxx/include/__format/parser_std_format_spec.h
--- a/libcxx/include/__format/parser_std_format_spec.h
+++ b/libcxx/include/__format/parser_std_format_spec.h
@@ -52,8 +52,12 @@
  * * The format-type filtering needs to be done post parsing in the parser
  *   derived from @ref __parser_std.
  */
-_LIBCPP_PACKED_BYTE_FOR_AIX
-class _LIBCPP_TYPE_VIS _Flags {
+#if defined(_AIX)
+class _LIBCPP_TYPE_VIS __attribute__((__packed__)) _Flags
+#else
+class _LIBCPP_TYPE_VIS _Flags
+#endif
+{
 public:
   enum class _LIBCPP_ENUM_VIS _Alignment : uint8_t {
     /**
@@ -110,7 +114,6 @@
 
   _Type __type{_Type::__default};
 };
-_LIBCPP_PACKED_BYTE_FOR_AIX_END
 
 namespace __detail {
 template <class _CharT>