Index: Ringtoets/StabilityPointStructures/src/Ringtoets.StabilityPointStructures.Service/StabilityPointStructuresCalculationService.cs
===================================================================
diff -u -rf7a0b62177d09fb02de673c29f7d153775c5608d -r4febca1a6186a1c6a09aa673ce967ff0b7efd0b1
--- Ringtoets/StabilityPointStructures/src/Ringtoets.StabilityPointStructures.Service/StabilityPointStructuresCalculationService.cs	(.../StabilityPointStructuresCalculationService.cs)	(revision f7a0b62177d09fb02de673c29f7d153775c5608d)
+++ Ringtoets/StabilityPointStructures/src/Ringtoets.StabilityPointStructures.Service/StabilityPointStructuresCalculationService.cs	(.../StabilityPointStructuresCalculationService.cs)	(revision 4febca1a6186a1c6a09aa673ce967ff0b7efd0b1)
@@ -160,7 +160,10 @@
         /// </summary>
         public void Cancel()
         {
-            calculator?.Cancel();
+            if (calculator != null)
+            {
+                calculator.Cancel();
+            }
             canceled = true;
         }