How to pack string into msgpack::object in C++?

Question

std::map<std::string, msgpack::object> msgpack; 
msgpack["string"] = msgpack::object("string"); 

undefined reference to void msgpack::v1::operator<< <char, 4ul>(msgpack::v2::object&, char const (&) [4ul])'`

I want to pack string into msgpack::object, but i got above error. How can I solve this?