diff --git a/clang/lib/Headers/__stddef_nullptr_t.h b/clang/lib/Headers/__stddef_nullptr_t.h
index 183d394d56c1b..f5fd9c12715e9 100644
--- a/clang/lib/Headers/__stddef_nullptr_t.h
+++ b/clang/lib/Headers/__stddef_nullptr_t.h
@@ -17,7 +17,9 @@ typedef decltype(nullptr) nullptr_t;
 }
 using ::std::nullptr_t;
 #endif
-#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L
+/* FIXME: This is using the placeholder dates Clang produces for these macros
+   in C2x mode; switch to the correct values once they've been published. */
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202000L
 typedef typeof(nullptr) nullptr_t;
 #endif