diff --git a/src/FakeXrmEasy.Core/Extensions/OptionSetValueCollectionExtensions.cs b/src/FakeXrmEasy.Core/Extensions/OptionSetValueCollectionExtensions.cs
index 7084a2db..1350712f 100644
--- a/src/FakeXrmEasy.Core/Extensions/OptionSetValueCollectionExtensions.cs
+++ b/src/FakeXrmEasy.Core/Extensions/OptionSetValueCollectionExtensions.cs
@@ -21,6 +21,8 @@ public static class OptionSetValueCollectionExtensions
         /// <returns></returns>
         public static HashSet<int> ConvertToHashSetOfInt(this object input, bool isOptionSetValueCollectionAccepted)
         {
+            if (input == null) return null;
+            
             var set = new HashSet<int>();
 
             var faultReason = $"The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter" +
diff --git a/tests/FakeXrmEasy.Core.Tests/Extensions/OptionSetValueCollectionExtensionsTests.cs b/tests/FakeXrmEasy.Core.Tests/Extensions/OptionSetValueCollectionExtensionsTests.cs
index ab8078ac..2f76b1e1 100644
--- a/tests/FakeXrmEasy.Core.Tests/Extensions/OptionSetValueCollectionExtensionsTests.cs
+++ b/tests/FakeXrmEasy.Core.Tests/Extensions/OptionSetValueCollectionExtensionsTests.cs
@@ -12,6 +12,12 @@ namespace FakeXrmEasy.Core.Tests.Extensions
 {
     public class OptionSetValueCollectionExtensionsTests
     {
+        [Fact]
+        public void Should_convert_to_null_if_null()
+        {
+            Assert.Null(OptionSetValueCollectionExtensions.ConvertToHashSetOfInt(null, true));
+        }
+
         [Fact]
         public void Should_convert_to_a_hash_of_int_from_an_option_set_value_collection()
         {