Index: Riskeer/Common/src/Riskeer.Common.Forms/ChangeHandlers/FailureMechanismPropertyChangeHandler.cs
===================================================================
diff -u -rd9119b8f4a74fb2a6f3ececeaea94f0e58513c52 -r98435e06d93b63f51f1d72c832baec370c7fcad9
--- Riskeer/Common/src/Riskeer.Common.Forms/ChangeHandlers/FailureMechanismPropertyChangeHandler.cs	(.../FailureMechanismPropertyChangeHandler.cs)	(revision d9119b8f4a74fb2a6f3ececeaea94f0e58513c52)
+++ Riskeer/Common/src/Riskeer.Common.Forms/ChangeHandlers/FailureMechanismPropertyChangeHandler.cs	(.../FailureMechanismPropertyChangeHandler.cs)	(revision 98435e06d93b63f51f1d72c832baec370c7fcad9)
@@ -37,7 +37,7 @@
     /// failure mechanism property.
     /// </summary>
     public class FailureMechanismPropertyChangeHandler<T> : IFailureMechanismPropertyChangeHandler<T>
-        where T : ICalculatableFailureMechanism
+        where T : class, ICalculatableFailureMechanism
     {
         public IEnumerable<IObservable> SetPropertyValueAfterConfirmation<TValue>(
             T failureMechanism,
Index: Riskeer/Common/src/Riskeer.Common.Forms/PropertyClasses/IFailureMechanismPropertyChangeHandler.cs
===================================================================
diff -u -rd9119b8f4a74fb2a6f3ececeaea94f0e58513c52 -r98435e06d93b63f51f1d72c832baec370c7fcad9
--- Riskeer/Common/src/Riskeer.Common.Forms/PropertyClasses/IFailureMechanismPropertyChangeHandler.cs	(.../IFailureMechanismPropertyChangeHandler.cs)	(revision d9119b8f4a74fb2a6f3ececeaea94f0e58513c52)
+++ Riskeer/Common/src/Riskeer.Common.Forms/PropertyClasses/IFailureMechanismPropertyChangeHandler.cs	(.../IFailureMechanismPropertyChangeHandler.cs)	(revision 98435e06d93b63f51f1d72c832baec370c7fcad9)
@@ -42,7 +42,7 @@
     /// failure mechanism property.
     /// </summary>
     /// <typeparam name="T">The type of the calculatable failure mechanism.</typeparam>
-    public interface IFailureMechanismPropertyChangeHandler<T> where T : ICalculatableFailureMechanism
+    public interface IFailureMechanismPropertyChangeHandler<T> where T : class, ICalculatableFailureMechanism
     {
         /// <summary>
         /// Find out whether the property can be updated with or without confirmation. If confirmation is required, 
Index: Riskeer/Common/test/Riskeer.Common.Forms.TestUtil/FailureMechanismSetPropertyValueAfterConfirmationParameterTester.cs
===================================================================
diff -u -rd9119b8f4a74fb2a6f3ececeaea94f0e58513c52 -r98435e06d93b63f51f1d72c832baec370c7fcad9
--- Riskeer/Common/test/Riskeer.Common.Forms.TestUtil/FailureMechanismSetPropertyValueAfterConfirmationParameterTester.cs	(.../FailureMechanismSetPropertyValueAfterConfirmationParameterTester.cs)	(revision d9119b8f4a74fb2a6f3ececeaea94f0e58513c52)
+++ Riskeer/Common/test/Riskeer.Common.Forms.TestUtil/FailureMechanismSetPropertyValueAfterConfirmationParameterTester.cs	(.../FailureMechanismSetPropertyValueAfterConfirmationParameterTester.cs)	(revision 98435e06d93b63f51f1d72c832baec370c7fcad9)
@@ -34,7 +34,7 @@
     /// <typeparam name="TFailureMechanism">The type of the calculatable failure mechanism that is expected to be passed to the method.</typeparam>
     /// <typeparam name="TExpectedValue">The type of the value that is expected to be passed to the method.</typeparam>
     public class FailureMechanismSetPropertyValueAfterConfirmationParameterTester<TFailureMechanism, TExpectedValue> : IFailureMechanismPropertyChangeHandler<TFailureMechanism>
-        where TFailureMechanism : ICalculatableFailureMechanism
+        where TFailureMechanism : class, ICalculatableFailureMechanism
     {
         /// <summary>
         /// Creates a new instance of <see cref="FailureMechanismSetPropertyValueAfterConfirmationParameterTester{TFailureMechanism,TExpectedValue}"/>.