diff --git a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
index 72bd8442fd30..5ad55b99a1b3 100644
--- a/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
+++ b/llvm/utils/gn/secondary/libcxx/include/BUILD.gn
@@ -363,6 +363,7 @@ if (current_toolchain == default_toolchain) {
       "__format/format_args.h",
       "__format/format_context.h",
       "__format/format_error.h",
+      "__format/format_functions.h",
       "__format/format_fwd.h",
       "__format/format_parse_context.h",
       "__format/format_string.h",