Failing serialization of stronglytyped id in dictionary

TestClass.cs

public class TestClass
{
    [Fact]
    public void MyTestMethod()
    {
        var dict = new Dictionary<UserId, string>();
        var userId = UserId.New();

        dict[userId] = "Yolo";

        System.Text.Json.JsonSerializer.Serialize(dict);
    }
}

[StronglyTypedId(backingType: StronglyTypedIdBackingType.Guid)]
public readonly partial struct UserId
{
    public static UserId From(string id)
        => new(Guid.Parse(id));
}