Possible NullReferencePointer in for loop

Snippet

In the following code Reshaper gives a warning that curve[i] inside the for loop can be a possible NullReferenceException. Can I get rid of this without checking if curve[i] is null for every loop? As stated with annotations in the parameters, the curve can not contain items that are null.

public double Test([NotNull, ItemNotNull] List<Point2D> curve, double crossPoint)
{
    for (var i = 0; i < curve.Count - 1; i++)
    {
        if (curve[i].X >= crossPoint && curve[i + 1].X > crossPoint)
        {
            return curve[i].X;
        }
    }
 
    return double.NaN;
}