System.Text.Json deserialization not deserializing the Json string [duplicate]

We have a class as shown below:

public class KeyVal<Key, Val>
{
    public Key Id { get; set; }
    public Val Text { get; set; }

    
    public KeyVal() { }

    public KeyVal(Key key, Val val)
    {
        this.Id = key;
        this.Text = val;
    }
}

We are sending a Json string from the client using javascript to our controller action as follows:

[{"id":7.4,"text":false},{"id":9.0,"text":true}]

which when looked at the controller as an argument it looks perfectly ok and identical to what was sent:

[{"id":7.4,"text":false},{"id":9.0,"text":true}]

We are trying to deserialize this into the calss above using the following code:

var deserialized= System.Text.Json.JsonSerializer.Deserialize<List<KeyVal<float?, bool>>>(list)

But ufortunately we keep getting nulls for the id and always false for the text property. i.e. its not being deserialized into an instance of our class.

Any ideas?