How to set the float precision for the Json::FastWriter using C++ and jsoncpp

Question

I am accessing some json objects via a rest interface, by converting the Json::Value to a string and respond this string to the request.

std::string json_to_string(Json::Value& json_object) {
    Json::FastWriter fastWriter;
    return fastWriter.write(json_object);
}

Numeric values parsed from a float variable are looking like this

"float_value":0.089996337890625

How can I set a precision for the Json::FastWriter?

For saving the json object to the filesystem, I a found a simple solution, but I was not able to transfer this to the Json::FastWriter (which is necessary for the rest interface).

int save_json_file(std::string path, Json::Value json_object) {

    Json::Value root;
    Json::StreamWriterBuilder builder;
    builder["precision"] = 3; 
    const std::unique_ptr<Json::StreamWriter> writer(builder.newStreamWriter());

    std::ofstream ofs;
    ofs.open(path);
    writer->write(json_object, &ofs);

    return EXIT_SUCCESS;
}

Alternative suggestions are welcome!