Using map to connect string with enum

I created map that connects enum with strings in order to have easier times doing current project. Code looks like this:

struct responseMap : public std::map < std::string, CitizenType > {
    responseMap() {
        this->operator[]("slave") = CitizenType::slave;
        this->operator[]("trader") = CitizenType::trader;
        this->operator[]("priest") = CitizenType::priest;
        this->operator[]("scholar") = CitizenType::scholar;
        this->operator[]("soldier") = CitizenType::soldier;
        this->operator[]("archer") = CitizenType::archer;
        this->operator[]("swordsman") = CitizenType::swordsman;
        this->operator[]("emperor") = CitizenType::emperor;
    }
};

My enum is just these types, described in map. Everything works fine exept it doesn't count "slave" as a member of map. For instance if I write down the following code:

responseMap myMap;
std::cout<<myMap["slave"]<<" "<<myMap["trader"];

it would produce the following line: 0 1

My question is why this is happening as I am describing them the same way?

Edit: I am trying with normal map like this:

std::map<std::string, CitizenType> otherMap = {
    { "slave", CitizenType::slave },
    { "trader", CitizenType::trader },
    { "priest", CitizenType::priest },
    { "scholar", CitizenType::scholar },
    { "soldier", CitizenType::soldier },
    { "archer", CitizenType::archer },
    { "swordsman", CitizenType::swordsman },
    { "emperor", CitizenType::emperor },
};

And it still outputs the same values.