Index: Ringtoets/Integration/src/Ringtoets.Integration.Forms/PropertyClasses/FailureMechanismContributionContextProperties.cs
===================================================================
diff -u -r0916bc9808f7c527e16e75a5404b800d2bd223c5 -r0bf7bef98d08bd001d4c999443ce5f4e8761c674
--- Ringtoets/Integration/src/Ringtoets.Integration.Forms/PropertyClasses/FailureMechanismContributionContextProperties.cs	(.../FailureMechanismContributionContextProperties.cs)	(revision 0916bc9808f7c527e16e75a5404b800d2bd223c5)
+++ Ringtoets/Integration/src/Ringtoets.Integration.Forms/PropertyClasses/FailureMechanismContributionContextProperties.cs	(.../FailureMechanismContributionContextProperties.cs)	(revision 0bf7bef98d08bd001d4c999443ce5f4e8761c674)
@@ -80,6 +80,11 @@
             }
             set
             {
+                if (value < 100 || value > 1000000)
+                {
+                    throw new ArgumentOutOfRangeException("value", Resources.FailureMechanismContributionContextProperties_ReturnPeriod_Value_for_ReturnPeriod_Must_be_in_range_100_to_1000000);
+                }
+
                 if (value != 0 && normChangeHandler.ConfirmNormChange())
                 {
                     double newNormValue = 1.0/Convert.ToInt32(value);