Index: clang/lib/Headers/stdatomic.h
===================================================================
--- clang/lib/Headers/stdatomic.h
+++ clang/lib/Headers/stdatomic.h
@@ -17,8 +17,8 @@
  * explicitly disallows `stdatomic.h` in the C mode via an `#error`.  Fallback
  * to the clang resource header until that is fully supported.
  */
-#if __STDC_HOSTED__ &&                                                         \
-    __has_include_next(<stdatomic.h>) && !(defined(_MSC_VER) && !defined(__cplusplus))
+#if __STDC_HOSTED__ && __has_include_next(<stdatomic.h>)                        \
+    && !(defined(_MSC_VER) && __cplusplus-0 < 202002l)
 # include_next <stdatomic.h>
 #else