Index: DamClassic/trunk/src/Dam/Data/CalculationHelper.cs
===================================================================
diff -u -r874 -r1440
--- DamClassic/trunk/src/Dam/Data/CalculationHelper.cs	(.../CalculationHelper.cs)	(revision 874)
+++ DamClassic/trunk/src/Dam/Data/CalculationHelper.cs	(.../CalculationHelper.cs)	(revision 1440)
@@ -134,6 +134,9 @@
             parameters.CalculationOptions = mstabParameters.CalculationOptions;
             parameters.CalculationOptions.MinimalCircleDepth = location.MinimalCircleDepth;
 
+            if (location.ModelFactors.RequiredSafetyFactorStabilityInnerSlope == null)
+                location.ModelFactors.RequiredSafetyFactorStabilityInnerSlope = 1.0;
+
             parameters.ZoneAreas = new MStabZoneAreas
                                    {
                                        SafetyFactorZone1A = location.ModelFactors.RequiredSafetyFactorStabilityInnerSlope.Value,