diff --git a/SabreTools.Library/DatItems/DatItem.cs b/SabreTools.Library/DatItems/DatItem.cs
index edb03487..cdea54e8 100644
--- a/SabreTools.Library/DatItems/DatItem.cs
+++ b/SabreTools.Library/DatItems/DatItem.cs
@@ -634,9 +634,9 @@ namespace SabreTools.Library.DatItems
             #region OpenMSX
 
             // Filter on original
-            if (filter.Original.MatchesPositiveSet(Original.Content) == false)
+            if (filter.Original.MatchesPositiveSet(Original?.Content) == false)
                 return false;
-            if (filter.Original.MatchesNegativeSet(Original.Content) == true)
+            if (filter.Original.MatchesNegativeSet(Original?.Content) == true)
                 return false;
 
             // Filter on OpenMSX subtype