diff --git a/include/msgpack/adaptor/check_container_size.hpp b/include/msgpack/adaptor/check_container_size.hpp
index 5fcc1289..294c3ece 100644
--- a/include/msgpack/adaptor/check_container_size.hpp
+++ b/include/msgpack/adaptor/check_container_size.hpp
@@ -44,7 +44,7 @@ inline void check_container_size(std::size_t size) {
 }
 
 template <>
-inline void check_container_size<4>(std::size_t size) {
+inline void check_container_size<4>(std::size_t /*size*/) {
 }
 
 } // namespace detail