Index: Riskeer/Integration/src/Riskeer.Integration.IO/Helpers/ExportableModelRegistry.cs
===================================================================
diff -u -rd9119b8f4a74fb2a6f3ececeaea94f0e58513c52 -r3c4b11e7e42dca62a4bdea7179184a883e31d68e
--- Riskeer/Integration/src/Riskeer.Integration.IO/Helpers/ExportableModelRegistry.cs	(.../ExportableModelRegistry.cs)	(revision d9119b8f4a74fb2a6f3ececeaea94f0e58513c52)
+++ Riskeer/Integration/src/Riskeer.Integration.IO/Helpers/ExportableModelRegistry.cs	(.../ExportableModelRegistry.cs)	(revision 3c4b11e7e42dca62a4bdea7179184a883e31d68e)
@@ -52,6 +52,7 @@
         /// <typeparam name="TExportableModel">The type of exportable model that is registered with <typeparamref name="TModel"/>.</typeparam>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="model"/> is <c>null</c>.</exception>
         private static bool ContainsValue<TModel, TExportableModel>(IReadOnlyDictionary<TModel, TExportableModel> collection, TModel model)
+            where TModel : class
         {
             if (model == null)
             {
@@ -72,6 +73,8 @@
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="model"/> or <paramref name="exportableModel"/> is <c>null</c>.</exception>
         private static void Register<TModel, TExportableModel>(IDictionary<TModel, TExportableModel> collection, TModel model,
                                                                TExportableModel exportableModel)
+            where TModel : class
+            where TExportableModel : class
         {
             if (model == null)
             {
@@ -98,6 +101,7 @@
         /// <exception cref="ArgumentNullException">Thrown when any <paramref name="model"/> is <c>null</c>.</exception>
         /// <exception cref="InvalidOperationException">Thrown when no item was registered for <paramref name="model"/>.</exception>
         private static TExportableModel Get<TModel, TExportableModel>(IReadOnlyDictionary<TModel, TExportableModel> collection, TModel model)
+            where TModel : class
         {
             if (model == null)
             {
Index: Riskeer/Revetment/src/Riskeer.Revetment.Service/WaveConditionsDataSynchronizationService.cs
===================================================================
diff -u -rd9119b8f4a74fb2a6f3ececeaea94f0e58513c52 -r3c4b11e7e42dca62a4bdea7179184a883e31d68e
--- Riskeer/Revetment/src/Riskeer.Revetment.Service/WaveConditionsDataSynchronizationService.cs	(.../WaveConditionsDataSynchronizationService.cs)	(revision d9119b8f4a74fb2a6f3ececeaea94f0e58513c52)
+++ Riskeer/Revetment/src/Riskeer.Revetment.Service/WaveConditionsDataSynchronizationService.cs	(.../WaveConditionsDataSynchronizationService.cs)	(revision 3c4b11e7e42dca62a4bdea7179184a883e31d68e)
@@ -52,7 +52,7 @@
         /// <exception cref="NotSupportedException">Thrown when <paramref name="normativeProbabilityType"/> is not supported.</exception>
         public static IEnumerable<IObservable> ClearAllWaveConditionsCalculationOutput<TFailureMechanism, TCalculation>(
             TFailureMechanism failureMechanism, NormativeProbabilityType normativeProbabilityType)
-            where TFailureMechanism : ICalculatableFailureMechanism
+            where TFailureMechanism : class, ICalculatableFailureMechanism
             where TCalculation : ICalculation<WaveConditionsInput>
         {
             if (failureMechanism == null)
@@ -86,7 +86,7 @@
         /// <exception cref="ArgumentNullException">Thrown when any parameter is <c>null</c>.</exception>
         public static IEnumerable<IObservable> ClearAllWaveConditionsCalculationOutput<TFailureMechanism, TCalculation>(
             TFailureMechanism failureMechanism, HydraulicBoundaryLocationCalculationsForTargetProbability calculationsForTargetProbability)
-            where TFailureMechanism : ICalculatableFailureMechanism
+            where TFailureMechanism : class, ICalculatableFailureMechanism
             where TCalculation : ICalculation<WaveConditionsInput>
         {
             if (failureMechanism == null)
@@ -124,7 +124,7 @@
         /// <exception cref="ArgumentNullException">Thrown when any parameter is <c>null</c>.</exception>
         public static IEnumerable<IObservable> ClearWaveConditionsCalculationOutputAndRemoveTargetProbability<TFailureMechanism, TCalculation>(
             TFailureMechanism failureMechanism, HydraulicBoundaryLocationCalculationsForTargetProbability calculationsForTargetProbability)
-            where TFailureMechanism : ICalculatableFailureMechanism
+            where TFailureMechanism : class, ICalculatableFailureMechanism
             where TCalculation : ICalculation<WaveConditionsInput>
         {
             if (failureMechanism == null)