How to deserialize a JSON null value with the cereal C++ library?

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I’m using the C++ cereal library to handle JSON serialization/deserialization in my Android application. I saw that cereal added support for the std::optional type. So after targeting C++17 in my CMakeLists, I wrote a simple test case like this:

#include <string>
#include "cereal/types/optional.hpp"

struct SimpleObject {
    int present;
    std::optional<int> nullable;

    template<class Archive>
    void serialize(Archive &archive) {
        archive(present, nullable);
    }
};

int main() {
    string myJson = "{ \"present\": 1, \"nullable\": null }";

    stringstream is(myJson);
    SimpleObject simpleObject;
    {
        cereal::JSONInputArchive archive(is);
        simpleObject.serialize(archive);
    }

    return 0;
}

But my app is crashing with the following error: Abort message: 'terminating with uncaught exception of type cereal::RapidJSONException: rapidjson internal assertion failure: IsObject()'.

What am I doing wrong? Shouldn’t it work out of the box like I did?
Or is cereal expecting a JSON with another form?

I tried specifying a JSON string with only present being present and no other field, but then I’m getting this error: Abort message: 'terminating with uncaught exception of type cereal::Exception: No more objects in input'.

I also tried assigning a default std::nullopt value without success.

What’s weird is both cases should be valid JSON.

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