diff --git a/src/refwhenneeded.h b/src/refwhenneeded.h
index 30994ed..77b06fc 100644
--- a/src/refwhenneeded.h
+++ b/src/refwhenneeded.h
@@ -4,20 +4,33 @@
 #include <cstdint>
 
 namespace cpputils {
-template<typename X> struct RefWhenNeeded      { using T = const X &;     RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<bool>          { using T = bool;          RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<int8_t>        { using T = int8_t;        RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<uint8_t>       { using T = uint8_t;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<int16_t>       { using T = int16_t;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<uint16_t>      { using T = uint16_t;      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<int32_t>       { using T = int32_t;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<uint32_t>      { using T = uint32_t;      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<int64_t>       { using T = int64_t;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<uint64_t>      { using T = uint64_t;      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<long>          { using T = long;          RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<unsigned long> { using T = unsigned long; RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<float>         { using T = float;         RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-template<> struct RefWhenNeeded<double>        { using T = double;        RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<typename X> struct RefWhenNeeded                     { using T = const X &;                    RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<bool>                         { using T = bool;                         RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<int8_t>                       { using T = int8_t;                       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<uint8_t>                      { using T = uint8_t;                      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<int16_t>                      { using T = int16_t;                      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<uint16_t>                     { using T = uint16_t;                     RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<int32_t>                      { using T = int32_t;                      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<uint32_t>                     { using T = uint32_t;                     RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<int64_t>                      { using T = int64_t;                      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<uint64_t>                     { using T = uint64_t;                     RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<long>                         { using T = long;                         RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<unsigned long>                { using T = unsigned long;                RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<float>                        { using T = float;                        RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<double>                       { using T = double;                       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<bool>>          { using T = std::optional<bool>;          RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<int8_t>>        { using T = std::optional<int8_t>;        RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<uint8_t>>       { using T = std::optional<uint8_t>;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<int16_t>>       { using T = std::optional<int16_t>;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<uint16_t>>      { using T = std::optional<uint16_t>;      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<int32_t>>       { using T = std::optional<int32_t>;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<uint32_t>>      { using T = std::optional<uint32_t>;      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<int64_t>>       { using T = std::optional<int64_t>;       RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<uint64_t>>      { using T = std::optional<uint64_t>;      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<long>>          { using T = std::optional<long>;          RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<unsigned long>> { using T = std::optional<unsigned long>; RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<float>>         { using T = std::optional<float>;         RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
+template<> struct RefWhenNeeded<std::optional<double>>        { using T = std::optional<double>;        RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
 
 //template<typename X> struct RefWhenNeeded                       { using T = X;                                      RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
 //template<> struct RefWhenNeeded<JsonObjectConst>                { using T = const JsonObjectConst &;                RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
@@ -25,5 +38,4 @@ template<> struct RefWhenNeeded<double>        { using T = double;        RefWhe
 //template<> struct RefWhenNeeded<JsonArrayConst>                 { using T = const JsonArrayConst &;                 RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
 //template<> struct RefWhenNeeded<JsonVariantConst>               { using T = const JsonVariantConst &;               RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
 //template<> struct RefWhenNeeded<std::string>                    { using T = const std::string &;                    RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
-//template<> struct RefWhenNeeded<std::optional<uint32_t>>        { using T = const std::optional<uint32_t> &;        RefWhenNeeded() = delete; ~RefWhenNeeded() = delete; };
 } // namespace cpputils