Index: Ringtoets/GrassCoverErosionInwards/src/Ringtoets.GrassCoverErosionInwards.Data/GrassCoverErosionInwardsOutput.cs
===================================================================
diff -u -rcb9ea4ad53b55626245ff8399d7cf0905185e632 -rb4f7b17762bbc3631a79febf60076c6d5a2eabd4
--- Ringtoets/GrassCoverErosionInwards/src/Ringtoets.GrassCoverErosionInwards.Data/GrassCoverErosionInwardsOutput.cs	(.../GrassCoverErosionInwardsOutput.cs)	(revision cb9ea4ad53b55626245ff8399d7cf0905185e632)
+++ Ringtoets/GrassCoverErosionInwards/src/Ringtoets.GrassCoverErosionInwards.Data/GrassCoverErosionInwardsOutput.cs	(.../GrassCoverErosionInwardsOutput.cs)	(revision b4f7b17762bbc3631a79febf60076c6d5a2eabd4)
@@ -19,10 +19,9 @@
 // Stichting Deltares and remain full property of Stichting Deltares at all times.
 // All rights reserved.
 
+using System;
 using Core.Common.Base;
-using Core.Common.Base.Data;
 using Ringtoets.Common.Data.Calculation;
-using Ringtoets.Common.Data.Probability;
 
 namespace Ringtoets.GrassCoverErosionInwards.Data
 {
@@ -37,10 +36,16 @@
         /// <param name="resultOutput">The output of the assessment result.</param>
         /// <param name="dikeHeightOutput">The dike height output.</param>
         /// <param name="overtoppingRateOutput">The overtopping rate output.</param>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="resultOutput"/>
+        /// is <c>null</c>.</exception>
         public GrassCoverErosionInwardsOutput(GrassCoverErosionInwardsResultOutput resultOutput,
                                               DikeHeightOutput dikeHeightOutput,
                                               OvertoppingRateOutput overtoppingRateOutput)
         {
+            if (resultOutput == null)
+            {
+                throw new ArgumentNullException(nameof(resultOutput));
+            }
             ResultOutput = resultOutput;
             DikeHeightOutput = dikeHeightOutput;
             OvertoppingRateOutput = overtoppingRateOutput;
Index: Ringtoets/GrassCoverErosionInwards/test/Ringtoets.GrassCoverErosionInwards.Data.Test/GrassCoverErosionInwardsOutputTest.cs
===================================================================
diff -u -rcb9ea4ad53b55626245ff8399d7cf0905185e632 -rb4f7b17762bbc3631a79febf60076c6d5a2eabd4
--- Ringtoets/GrassCoverErosionInwards/test/Ringtoets.GrassCoverErosionInwards.Data.Test/GrassCoverErosionInwardsOutputTest.cs	(.../GrassCoverErosionInwardsOutputTest.cs)	(revision cb9ea4ad53b55626245ff8399d7cf0905185e632)
+++ Ringtoets/GrassCoverErosionInwards/test/Ringtoets.GrassCoverErosionInwards.Data.Test/GrassCoverErosionInwardsOutputTest.cs	(.../GrassCoverErosionInwardsOutputTest.cs)	(revision b4f7b17762bbc3631a79febf60076c6d5a2eabd4)
@@ -19,6 +19,7 @@
 // Stichting Deltares and remain full property of Stichting Deltares at all times.
 // All rights reserved.
 
+using System;
 using Core.Common.Base;
 using NUnit.Framework;
 using Ringtoets.Common.Data.Calculation;
@@ -32,6 +33,20 @@
     public class GrassCoverErosionInwardsOutputTest
     {
         [Test]
+        public void Constructor_ResultOutputNull_ThrowArgumentNullException()
+        {
+            // Call
+            TestDelegate test = () => new GrassCoverErosionInwardsOutput(
+                null,
+                new TestDikeHeightOutput(double.NaN),
+                new TestOvertoppingRateOutput(double.NaN));
+
+            // Assert
+            var exception = Assert.Throws<ArgumentNullException>(test);
+            Assert.AreEqual("resultOutput", exception.ParamName);
+        }
+
+        [Test]
         public void ParameteredConstructor_DefaultValues()
         {
             // Setup