diff --git a/libcxx/test/libcxx/system_reserved_names.gen.py b/libcxx/test/libcxx/system_reserved_names.gen.py
index f8589f2beaae3..d69182d68e0de 100644
--- a/libcxx/test/libcxx/system_reserved_names.gen.py
+++ b/libcxx/test/libcxx/system_reserved_names.gen.py
@@ -10,6 +10,13 @@
 # alphabetic macros. Also ensure that we don't swallow the definition of user
 # provided macros (in other words, ensure that we push/pop correctly everywhere).
 
+# This test fails with MSVC headers, with Clang 20 (and early 21 versions);
+# the headers end up pulling in Clang intrinsics headers, which in 20.x and
+# early 21.x versions use unreserved identifiers,
+# see https://github.com/llvm/llvm-project/issues/161808.
+#
+# UNSUPPORTED: clang-20 && msvc
+
 # RUN: %{python} %s %{libcxx-dir}/utils
 # END.