diff --git a/json/tree.hpp b/json/tree.hpp
index 8ac12abc..d8d723a9 100644
--- a/json/tree.hpp
+++ b/json/tree.hpp
@@ -350,10 +350,13 @@ namespace json::tree {
     // Instantiate this template for the type you wish to output. We use a
     // helper class here to avoid partial template specialisation of a
     // function (eg, for templated types).
-    template <typename T>
+    template <typename T, typename ...Args>
     struct io {
-        static std::unique_ptr<json::tree::node> serialise (const T&);
-        static T deserialise (const json::tree::node&);
+        static std::unique_ptr<json::tree::node>
+        serialise (const T&, Args &&...args);
+
+        static T
+        deserialise (const json::tree::node&, Args &&...args);
     };
 }
 
@@ -363,7 +366,7 @@ template <typename T, class ...Args>
 std::unique_ptr<json::tree::node>
 to_json (const T &t, Args&&... args)
 {
-    return json::tree::io<T>::serialise (
+    return json::tree::io<T,Args...>::serialise (
         t, std::forward<Args>(args)...
     );
 }
@@ -374,7 +377,7 @@ template <typename T, class ...Args>
 T
 from_json (const json::tree::node &n, Args&&... args)
 {
-    return json::tree::io<T>::deserialise (
+    return json::tree::io<T,Args...>::deserialise (
         n, std::forward<Args>(args)...
     );
 }
@@ -385,7 +388,7 @@ template <typename T, class ...Args>
 T
 from_json (const std::experimental::filesystem::path &src, Args &&...args)
 {
-    return from_json<T> (
+    return from_json<T,Args...> (
         *json::tree::parse (src),
         std::forward<Args> (args)...
     );