Index: Demo/Ringtoets/src/Demo.Ringtoets/Commands/AddNewDemoAssessmentSectionCommand.cs
===================================================================
diff -u -r20e9bfea15dfe132ee137283a9f24bc4c413ce4a -reabf1a800431a23b06c8d81dfbf0f46a71bb659b
--- Demo/Ringtoets/src/Demo.Ringtoets/Commands/AddNewDemoAssessmentSectionCommand.cs	(.../AddNewDemoAssessmentSectionCommand.cs)	(revision 20e9bfea15dfe132ee137283a9f24bc4c413ce4a)
+++ Demo/Ringtoets/src/Demo.Ringtoets/Commands/AddNewDemoAssessmentSectionCommand.cs	(.../AddNewDemoAssessmentSectionCommand.cs)	(revision eabf1a800431a23b06c8d81dfbf0f46a71bb659b)
@@ -451,7 +451,10 @@
         {
             ClosingStructuresFailureMechanism failureMechanism = demoAssessmentSection.ClosingStructures;
             ClosingStructure closingStructure = CreateDemoClosingStructure();
-            failureMechanism.ClosingStructures.Add(closingStructure);
+            failureMechanism.ClosingStructures.AddRange(new[]
+            {
+                closingStructure
+            }, "closingStructurePath");
 
             var calculation = new StructuresCalculation<ClosingStructuresInput>();
             failureMechanism.CalculationsGroup.Children.Add(calculation);