diff --git a/include/ylt/standalone/iguana/dynamic.hpp b/include/ylt/standalone/iguana/dynamic.hpp
index 47cf20154..898c53461 100644
--- a/include/ylt/standalone/iguana/dynamic.hpp
+++ b/include/ylt/standalone/iguana/dynamic.hpp
@@ -12,7 +12,12 @@ constexpr inline uint8_t ENABLE_ALL = 0x0F;
 
 template <typename T, uint8_t ENABLE_FLAG = ENABLE_PB>
 struct base_impl : public base {
-  base_impl() { [[maybe_unused]] static bool r = register_type<T>(); }
+  base_impl() {
+    // make sure init T before main, and can register_type before main.
+    [[maybe_unused]] static auto t =
+        ylt::reflection::internal::wrapper<T>::value;
+    [[maybe_unused]] static bool r = register_type<T>();
+  }
   void to_pb(std::string& str) const override {
     if constexpr ((ENABLE_FLAG & ENABLE_PB) != 0) {
       to_pb_adl((iguana_adl_t*)nullptr, *(static_cast<T const*>(this)), str);
diff --git a/include/ylt/standalone/iguana/json_writer.hpp b/include/ylt/standalone/iguana/json_writer.hpp
index 1901d565b..75d4a70e9 100644
--- a/include/ylt/standalone/iguana/json_writer.hpp
+++ b/include/ylt/standalone/iguana/json_writer.hpp
@@ -12,8 +12,9 @@ template <bool Is_writing_escape = true, typename Stream, typename T,
           std::enable_if_t<ylt_refletable_v<T>, int> = 0>
 IGUANA_INLINE void to_json(T &&t, Stream &s);
 namespace detail {
-template <bool Is_writing_escape = true, typename Stream, typename T>
-IGUANA_INLINE void to_json_impl(Stream &ss, const std::optional<T> &val);
+template <bool Is_writing_escape = true, typename Stream, typename T,
+          std::enable_if_t<optional_v<T>, int> = 0>
+IGUANA_INLINE void to_json_impl(Stream &ss, const T &val);
 
 template <bool Is_writing_escape = true, typename Stream, typename T,
           std::enable_if_t<fixed_array_v<T>, int> = 0>
@@ -151,8 +152,9 @@ IGUANA_INLINE void to_json_impl(Stream &ss, T val) {
   }
 }
 
-template <bool Is_writing_escape, typename Stream, typename T>
-IGUANA_INLINE void to_json_impl(Stream &ss, const std::optional<T> &val) {
+template <bool Is_writing_escape, typename Stream, typename T,
+          std::enable_if_t<optional_v<T>, int>>
+IGUANA_INLINE void to_json_impl(Stream &ss, const T &val) {
   if (!val) {
     ss.append("null");
   }
diff --git a/include/ylt/standalone/iguana/util.hpp b/include/ylt/standalone/iguana/util.hpp
index 614040cc0..8c3fca9e2 100644
--- a/include/ylt/standalone/iguana/util.hpp
+++ b/include/ylt/standalone/iguana/util.hpp
@@ -47,8 +47,7 @@ template <typename T>
 inline constexpr bool enum_v = std::is_enum_v<std::decay_t<T>>;
 
 template <typename T>
-constexpr inline bool optional_v =
-    is_template_instant_of<std::optional, std::remove_cvref_t<T>>::value;
+constexpr inline bool optional_v = ylt::reflection::optional<T>;
 
 template <class, class = void>
 struct is_container : std::false_type {};