diff --git a/core/apply.hh b/core/apply.hh
index 2201f0b96a..1419bcfa60 100644
--- a/core/apply.hh
+++ b/core/apply.hh
@@ -36,6 +36,7 @@ struct apply_helper<Func, std::tuple<T...>, std::index_sequence<I...>> {
 };
 
 template <typename Func, typename... T>
+inline
 auto apply(Func func, std::tuple<T...>&& args) {
     using helper = apply_helper<Func, std::tuple<T...>, std::index_sequence_for<T...>>;
     return helper::apply(std::move(func), std::move(args));