diff --git a/SabreTools.Helper/Dats/Partials/DatFile.Manipulate.cs b/SabreTools.Helper/Dats/Partials/DatFile.Manipulate.cs
index dbf09c91..6e1e5975 100644
--- a/SabreTools.Helper/Dats/Partials/DatFile.Manipulate.cs
+++ b/SabreTools.Helper/Dats/Partials/DatFile.Manipulate.cs
@@ -72,6 +72,10 @@ namespace SabreTools.Helper.Dats
 									{
 										newkey = newkey.ToLowerInvariant();
 									}
+									if (newkey == null)
+									{
+										newkey = "null";
+									}
 
 									newkey = HttpUtility.HtmlEncode(newkey);
 									break;