Blazor.Diagrams: Nullreference exception when adding link model target/source ports

For some reason the following code throws a NRE Am I doing something wrong?

            Diagram.Nodes.Add(current);

            if (parent is not null)
            {
                var link = new LinkModel(parent, current)
                {
                    TargetMarker = LinkMarker.Arrow
                };
                link.SetSourcePort(parent.GetPort(PortAlignment.Bottom));
                link.SetTargetPort(current.GetPort(PortAlignment.Top));
                Diagram.Links.Add(link);
            }

Stacktrace:

   at Blazor.Diagrams.Core.Layers.LinkLayer.OnItemAdded(BaseLinkModel link)
   at Blazor.Diagrams.Core.BaseLayer`1.Add(T item)
   at ForkHierarchy.Pages.Index.<RenderNodeAsync>d__24.MoveNext()

Checking whether I am adding a null value to SetSource/TargetPort, shows me that they do have values: