diff --git a/libcxx/.clang-format b/libcxx/.clang-format
index a6154c7c4a2bc..f548119652c19 100644
--- a/libcxx/.clang-format
+++ b/libcxx/.clang-format
@@ -30,6 +30,7 @@ AttributeMacros: [
                   '_LIBCPP_DEPRECATED_IN_CXX20',
                   '_LIBCPP_DEPRECATED_IN_CXX23',
                   '_LIBCPP_DEPRECATED',
+                  '_LIBCPP_DISABLE_EXTENSION_WARNING',
                   '_LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION',
                   '_LIBCPP_EXPORTED_FROM_ABI',
                   '_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS',