diff --git a/iguana/dynamic.hpp b/iguana/dynamic.hpp
index 74cc2da3..4b479b0c 100644
--- a/iguana/dynamic.hpp
+++ b/iguana/dynamic.hpp
@@ -17,9 +17,9 @@ constexpr inline uint8_t ENABLE_ALL = 0x0F;
 
 template <typename T, uint8_t ENABLE_FLAG = ENABLE_PB>
 struct base_impl : public base {
-  void to_pb(std::string& str) override {
+  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*>(this)), str);
+      to_pb_adl((iguana_adl_t*)nullptr, *(static_cast<T const*>(this)), str);
     }
     else {
       throw std::runtime_error("Protobuf Disabled");
@@ -160,7 +160,7 @@ struct base_impl : public base {
 
   virtual ~base_impl() {}
 
-  size_t cache_size = 0;
+  mutable size_t cache_size = 0;
 };
 
 IGUANA_INLINE std::shared_ptr<base> create_instance(std::string_view name) {
diff --git a/iguana/pb_util.hpp b/iguana/pb_util.hpp
index 5fa7365c..9ef8212c 100644
--- a/iguana/pb_util.hpp
+++ b/iguana/pb_util.hpp
@@ -73,8 +73,8 @@ constexpr inline WireType get_wire_type() {
 }
 
 template <typename T>
-constexpr bool is_lenprefix_v = (get_wire_type<T>() ==
-                                 WireType::LengthDelimeted);
+constexpr bool is_lenprefix_v =
+    (get_wire_type<T>() == WireType::LengthDelimeted);
 
 [[nodiscard]] IGUANA_INLINE uint32_t encode_zigzag(int32_t v) {
   return (static_cast<uint32_t>(v) << 1U) ^
@@ -419,6 +419,7 @@ IGUANA_INLINE size_t pb_oneof_size(Type&& t, Arr& size_arr) {
   int len = 0;
   std::visit(
       [&len, &size_arr](auto&& value) IGUANA__INLINE_LAMBDA {
+        using raw_value_type = decltype(value);
         using value_type =
             std::remove_const_t<std::remove_reference_t<decltype(value)>>;
         constexpr auto offset =
@@ -427,7 +428,7 @@ IGUANA_INLINE size_t pb_oneof_size(Type&& t, Arr& size_arr) {
             ((field_no + offset) << 3) |
             static_cast<uint32_t>(get_wire_type<value_type>());
         len = pb_key_value_size<variant_uint32_size_constexpr(key), false>(
-            std::forward<value_type>(value), size_arr);
+            std::forward<raw_value_type>(value), size_arr);
       },
       std::forward<Type>(t));
   return len;
@@ -454,7 +455,7 @@ IGUANA_INLINE size_t pb_key_value_size(Type&& t, Arr& size_arr) {
                                    std::decay_t<decltype(tuple)>>;
           constexpr auto value = std::get<decltype(i)::value>(tuple);
           using U = typename field_type::value_type;
-          auto& val = value.value(t);
+          auto const& val = value.value(t);
           if constexpr (variant_v<U>) {
             constexpr auto offset =
                 get_variant_index<U, typename field_type::sub_type,
diff --git a/iguana/pb_writer.hpp b/iguana/pb_writer.hpp
index 4c39305a..219650fb 100644
--- a/iguana/pb_writer.hpp
+++ b/iguana/pb_writer.hpp
@@ -83,6 +83,7 @@ IGUANA_INLINE void to_pb_oneof(Type&& t, It&& it, uint32_t*& sz_ptr) {
   using T = std::decay_t<Type>;
   std::visit(
       [&it, &sz_ptr](auto&& value) IGUANA__INLINE_LAMBDA {
+        using raw_value_type = decltype(value);
         using value_type =
             std::remove_const_t<std::remove_reference_t<decltype(value)>>;
         constexpr auto offset =
@@ -90,7 +91,7 @@ IGUANA_INLINE void to_pb_oneof(Type&& t, It&& it, uint32_t*& sz_ptr) {
         constexpr uint32_t key =
             ((field_no + offset) << 3) |
             static_cast<uint32_t>(get_wire_type<value_type>());
-        to_pb_impl<key, false>(std::forward<value_type>(value), it, sz_ptr);
+        to_pb_impl<key, false>(std::forward<raw_value_type>(value), it, sz_ptr);
       },
       std::forward<Type>(t));
 }
@@ -449,7 +450,7 @@ IGUANA_INLINE void build_sub_proto(Map& map, std::string_view str_type,
 }  // namespace detail
 
 template <typename T, typename Stream>
-IGUANA_INLINE void to_pb(T& t, Stream& out) {
+IGUANA_INLINE void to_pb(T const& t, Stream& out) {
   std::vector<uint32_t> size_arr;
   auto byte_len = detail::pb_key_value_size<0>(t, size_arr);
   detail::resize(out, byte_len);
@@ -491,7 +492,7 @@ IGUANA_INLINE void to_proto_file(Stream& stream, std::string_view ns = "") {
 #endif
 
 template <typename T, typename Stream>
-IGUANA_INLINE void to_pb_adl(iguana_adl_t* p, T& t, Stream& out) {
+IGUANA_INLINE void to_pb_adl(iguana_adl_t* p, T const& t, Stream& out) {
   to_pb(t, out);
 }
 
diff --git a/iguana/reflection.hpp b/iguana/reflection.hpp
index df3ea91c..6bad499c 100644
--- a/iguana/reflection.hpp
+++ b/iguana/reflection.hpp
@@ -562,7 +562,7 @@ struct field_info {
 };
 
 struct base {
-  virtual void to_pb(std::string &str) {}
+  virtual void to_pb(std::string &str) const {}
   virtual void from_pb(std::string_view str) {}
   virtual void to_xml(std::string &str) const {}
   virtual void from_xml(std::string_view str) {}
@@ -803,6 +803,7 @@ struct field_t {
   uint32_t field_no;
 
   auto &value(owner_type &value) const { return value.*member_ptr; }
+  auto const &value(owner_type const &value) const { return value.*member_ptr; }
 };
 
 template <typename T>