Index: Ringtoets/Piping/src/Ringtoets.Piping.Data/DerivedPipingInput.cs
===================================================================
diff -u -r3254da22c99c7eb680cdb838519684ce314afb0a -r124e30d6f914a8e154ae8de0827ca363c89bba64
--- Ringtoets/Piping/src/Ringtoets.Piping.Data/DerivedPipingInput.cs	(.../DerivedPipingInput.cs)	(revision 3254da22c99c7eb680cdb838519684ce314afb0a)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Data/DerivedPipingInput.cs	(.../DerivedPipingInput.cs)	(revision 124e30d6f914a8e154ae8de0827ca363c89bba64)
@@ -283,8 +283,11 @@
                 numberOfDecimals))
             {
                 PipingSoilLayer topMostAquiferLayer = aquiferLayers.First();
-                double deviationFraction = (topMostAquiferLayer.PermeabilityDeviation / topMostAquiferLayer.PermeabilityMean);
 
+                var permeabilityDeviation = new RoundedDouble(numberOfDecimals, topMostAquiferLayer.PermeabilityDeviation);
+                var permeabilityMean = new RoundedDouble(numberOfDecimals, topMostAquiferLayer.PermeabilityMean);
+                double deviationFraction = (permeabilityDeviation / permeabilityMean);
+
                 var weightedMean = new RoundedDouble(numberOfDecimals,
                                                      GetWeightedMeanForDarcyPermeabilityOfAquiferLayer(aquiferLayers,
                                                                                                        input.StochasticSoilProfile.SoilProfile,
@@ -374,7 +377,7 @@
                 return true;
             }
 
-            return distributions.All(currentLayerDistribution => AreDeviationAndFractionEqual(
+            return distributions.All(currentLayerDistribution => AreDeviationAndMeanFractionEqual(
                 currentLayerDistribution,
                 distributions[0]));
         }
@@ -418,7 +421,7 @@
                    currentLayerDistribution.Shift == baseLayerDistribution.Shift;
         }
 
-        private static bool AreDeviationAndFractionEqual(LogNormalDistribution currentLayerDistribution, LogNormalDistribution baseLayerDistribution)
+        private static bool AreDeviationAndMeanFractionEqual(LogNormalDistribution currentLayerDistribution, LogNormalDistribution baseLayerDistribution)
         {
             var baseLayerDeviationFraction = (baseLayerDistribution.StandardDeviation / baseLayerDistribution.Mean);
             var currentLayerDeviationFraction = (currentLayerDistribution.StandardDeviation / currentLayerDistribution.Mean);