Index: libcxx/include/__config
===================================================================
--- libcxx/include/__config
+++ libcxx/include/__config
@@ -953,7 +953,7 @@
 #define _LIBCPP_WCTYPE_IS_MASK
 #endif

-#if _LIBCPP_STD_VER <= 17 || !defined(__cpp_char8_t)
+#if _LIBCPP_STD_VER <= 17 && !defined(__cpp_char8_t)
 #define _LIBCPP_NO_HAS_CHAR8_T
 #endif