diff --git a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
index a77a0ff2d33b01..6bf558e25ab923 100644
--- a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
@@ -19,6 +19,7 @@ if (current_toolchain == default_toolchain) {
       "_LIBCPP_ABI_FORCE_ITANIUM=",
       "_LIBCPP_ABI_FORCE_MICROSOFT=",
       "_LIBCPP_EXTRA_SITE_DEFINES=",
+      "_LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT=",
       "_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY=",
       "_LIBCPP_HAS_NO_INCOMPLETE_FORMAT=",
       "_LIBCPP_HAS_NO_INCOMPLETE_RANGES=",