diff --git a/AsbCloudApp/AsbCloudApp.csproj b/AsbCloudApp/AsbCloudApp.csproj
index 11ffe050..79ec9867 100644
--- a/AsbCloudApp/AsbCloudApp.csproj
+++ b/AsbCloudApp/AsbCloudApp.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
 	<GenerateDocumentationFile>true</GenerateDocumentationFile>
-	<Nullable>disable</Nullable>
+	<Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/AsbCloudApp/Comparators/ComparerIId.cs b/AsbCloudApp/Comparators/ComparerIId.cs
index 7dbf5cb5..93b0d91a 100644
--- a/AsbCloudApp/Comparators/ComparerIId.cs
+++ b/AsbCloudApp/Comparators/ComparerIId.cs
@@ -9,7 +9,7 @@ namespace AsbCloudApp.Comparators
     /// </summary>
     public class ComparerIId : IComparer<IId>, IEqualityComparer<IId>
     {
-        private static readonly ComparerIId instance = new ();
+        private static readonly ComparerIId instance = new();
         private ComparerIId() { }
 
         /// <summary>
@@ -24,8 +24,13 @@ namespace AsbCloudApp.Comparators
         /// <param name="x"></param>
         /// <param name="y"></param>
         /// <returns></returns>
-        public int Compare(IId x, IId y) =>
-            x.Id.CompareTo(y.Id);
+        public int Compare(IId? x, IId? y)
+        {
+            if (x is null || y is null)
+                return 0;
+            else
+                return x.Id.CompareTo(y.Id);
+        }
 
         /// <summary>
         /// 
@@ -33,8 +38,13 @@ namespace AsbCloudApp.Comparators
         /// <param name="x"></param>
         /// <param name="y"></param>
         /// <returns></returns>
-        public bool Equals(IId x, IId y) =>
-            x.Id == y.Id;
+        public bool Equals(IId? x, IId? y)
+        {
+            if (x is null || y is null)
+                return false;
+            else
+                return x.Id == y.Id;
+        }
 
         /// <summary>
         ///