diff --git a/include/scan_helper.h b/include/scan_helper.h
index c5ecdd5..49f1b6b 100644
--- a/include/scan_helper.h
+++ b/include/scan_helper.h
@@ -346,10 +346,12 @@ scan_border(border_node** const target, const std::string_view l_key,
                     tuple_list.emplace_back(std::make_tuple(
                             full_key, static_cast<ValueType*>(value::get_body(vp))));
                 } else if constexpr (NeedSize) {
+                    (void)full_key; // cannot use [[maybe_unused]] for lambda capture
                     tuple_list.emplace_back(std::make_tuple(
                             static_cast<ValueType*>(value::get_body(vp)),
                             value::get_len(vp)));
                 } else {
+                    (void)full_key; // cannot use [[maybe_unused]] for lambda capture
                     tuple_list.emplace_back(
                             static_cast<ValueType*>(value::get_body(vp)));
                 }