Index: Ringtoets/Piping/src/Ringtoets.Piping.Plugin/PipingGuiPlugin.cs
===================================================================
diff -u -r39ad631dab6b2ae544ccdabf22fad6b4e5493218 -rf5fba362fd622350af428420089c20f80f218b78
--- Ringtoets/Piping/src/Ringtoets.Piping.Plugin/PipingGuiPlugin.cs	(.../PipingGuiPlugin.cs)	(revision 39ad631dab6b2ae544ccdabf22fad6b4e5493218)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Plugin/PipingGuiPlugin.cs	(.../PipingGuiPlugin.cs)	(revision f5fba362fd622350af428420089c20f80f218b78)
@@ -85,7 +85,7 @@
                 OnNodeRenamed = PipingCalculationContextOnNodeRenamed,
                 CanRemove = PipingCalculationContextCanRemove,
                 OnNodeRemoved = PipingCalculationContextOnNodeRemoved,
-                CanDrag = (pipingCalculationContext, sourceNode) => DragOperations.Move
+                CanDrag = (pipingCalculationContext, parentData) => DragOperations.Move
             };
 
             yield return new TreeNodeInfo<PipingCalculationGroupContext>
@@ -102,7 +102,7 @@
                 CanDrag = PipingCalculationGroupContextCanDrag,
                 CanDrop = PipingCalculationGroupContextCanDrop,
                 CanInsert = PipingCalculationGroupContextCanInsert,
-                OnDrop = PipingCalculationGroupContextOnDrop,
+                OnDrop = PipingCalculationGroupContextOnDrop
             };
 
             yield return new TreeNodeInfo<PipingInputContext>
@@ -690,9 +690,9 @@
             }
         }
 
-        private DragOperations PipingCalculationGroupContextCanDrag(PipingCalculationGroupContext nodeData, TreeNode sourceNode)
+        private DragOperations PipingCalculationGroupContextCanDrag(PipingCalculationGroupContext nodeData, object parentData)
         {
-            if (sourceNode.Parent.Tag is PipingFailureMechanism)
+            if (parentData is PipingFailureMechanism)
             {
                 return DragOperations.None;
             }