diff --git a/src/Avalonia.Controls/SelectionModelChangeSet.cs b/src/Avalonia.Controls/SelectionModelChangeSet.cs
index c0228a1cbc..57bf369585 100644
--- a/src/Avalonia.Controls/SelectionModelChangeSet.cs
+++ b/src/Avalonia.Controls/SelectionModelChangeSet.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
 
+#nullable enable
+
 namespace Avalonia.Controls
 {
     internal class SelectionModelChangeSet
@@ -31,11 +33,11 @@ namespace Avalonia.Controls
                 _changes,
                 selectedCount,
                 GetSelectedIndexAt);
-            var deselectedItems = new SelectedItems<object, SelectionNodeOperation>(
+            var deselectedItems = new SelectedItems<object?, SelectionNodeOperation>(
                 _changes,
                 deselectedCount,
                 GetDeselectedItemAt);
-            var selectedItems = new SelectedItems<object, SelectionNodeOperation>(
+            var selectedItems = new SelectedItems<object?, SelectionNodeOperation>(
                 _changes,
                 selectedCount,
                 GetSelectedItemAt);
@@ -52,7 +54,7 @@ namespace Avalonia.Controls
             int index)
         {
             static int GetCount(SelectionNodeOperation info) => info.DeselectedCount;
-            static List<IndexRange> GetRanges(SelectionNodeOperation info) => info.DeselectedRanges;
+            static List<IndexRange>? GetRanges(SelectionNodeOperation info) => info.DeselectedRanges;
             return GetIndexAt(infos, index, GetCount, GetRanges);
         }
 
@@ -61,25 +63,25 @@ namespace Avalonia.Controls
             int index)
         {
             static int GetCount(SelectionNodeOperation info) => info.SelectedCount;
-            static List<IndexRange> GetRanges(SelectionNodeOperation info) => info.SelectedRanges;
+            static List<IndexRange>? GetRanges(SelectionNodeOperation info) => info.SelectedRanges;
             return GetIndexAt(infos, index, GetCount, GetRanges);
         }
 
-        private object GetDeselectedItemAt(
+        private object? GetDeselectedItemAt(
             List<SelectionNodeOperation> infos,
             int index)
         {
             static int GetCount(SelectionNodeOperation info) => info.DeselectedCount;
-            static List<IndexRange> GetRanges(SelectionNodeOperation info) => info.DeselectedRanges;
+            static List<IndexRange>? GetRanges(SelectionNodeOperation info) => info.DeselectedRanges;
             return GetItemAt(infos, index, GetCount, GetRanges);
         }
 
-        private object GetSelectedItemAt(
+        private object? GetSelectedItemAt(
             List<SelectionNodeOperation> infos,
             int index)
         {
             static int GetCount(SelectionNodeOperation info) => info.SelectedCount;
-            static List<IndexRange> GetRanges(SelectionNodeOperation info) => info.SelectedRanges;
+            static List<IndexRange>? GetRanges(SelectionNodeOperation info) => info.SelectedRanges;
             return GetItemAt(infos, index, GetCount, GetRanges);
         }
 
@@ -87,7 +89,7 @@ namespace Avalonia.Controls
             List<SelectionNodeOperation> infos,
             int index,
             Func<SelectionNodeOperation, int> getCount,
-            Func<SelectionNodeOperation, List<IndexRange>> getRanges)
+            Func<SelectionNodeOperation, List<IndexRange>?> getRanges)
         {
             var currentIndex = 0;
             IndexPath path = default;
@@ -109,14 +111,14 @@ namespace Avalonia.Controls
             return path;
         }
 
-        private object GetItemAt(
+        private object? GetItemAt(
             List<SelectionNodeOperation> infos,
             int index,
             Func<SelectionNodeOperation, int> getCount,
-            Func<SelectionNodeOperation, List<IndexRange>> getRanges)
+            Func<SelectionNodeOperation, List<IndexRange>?> getRanges)
         {
             var currentIndex = 0;
-            object item = null;
+            object? item = null;
 
             foreach (var info in infos)
             {
@@ -125,7 +127,7 @@ namespace Avalonia.Controls
                 if (index >= currentIndex && index < currentIndex + currentCount)
                 {
                     int targetIndex = GetIndexAt(getRanges(info), index - currentIndex);
-                    item = info.Items.GetAt(targetIndex);
+                    item = info.Items?.GetAt(targetIndex);
                     break;
                 }
 
@@ -135,20 +137,23 @@ namespace Avalonia.Controls
             return item;
         }
 
-        private int GetIndexAt(List<IndexRange> ranges, int index)
+        private int GetIndexAt(List<IndexRange>? ranges, int index)
         {
             var currentIndex = 0;
 
-            foreach (var range in ranges)
+            if (ranges != null)
             {
-                var currentCount = (range.End - range.Begin) + 1;
-
-                if (index >= currentIndex && index < currentIndex + currentCount)
+                foreach (var range in ranges)
                 {
-                    return range.Begin + (index - currentIndex);
-                }
+                    var currentCount = (range.End - range.Begin) + 1;
 
-                currentIndex += currentCount;
+                    if (index >= currentIndex && index < currentIndex + currentCount)
+                    {
+                        return range.Begin + (index - currentIndex);
+                    }
+
+                    currentIndex += currentCount;
+                }
             }
 
             throw new IndexOutOfRangeException();
diff --git a/src/Avalonia.Controls/SelectionModelSelectionChangedEventArgs.cs b/src/Avalonia.Controls/SelectionModelSelectionChangedEventArgs.cs
index 4e64ee6e6f..5e2efdf331 100644
--- a/src/Avalonia.Controls/SelectionModelSelectionChangedEventArgs.cs
+++ b/src/Avalonia.Controls/SelectionModelSelectionChangedEventArgs.cs
@@ -15,13 +15,13 @@ namespace Avalonia.Controls
         public SelectionModelSelectionChangedEventArgs(
             IReadOnlyList<IndexPath>? deselectedIndices,
             IReadOnlyList<IndexPath>? selectedIndices,
-            IReadOnlyList<object>? deselectedItems,
-            IReadOnlyList<object>? selectedItems)
+            IReadOnlyList<object?>? deselectedItems,
+            IReadOnlyList<object?>? selectedItems)
         {
             DeselectedIndices = deselectedIndices ?? Array.Empty<IndexPath>();
             SelectedIndices = selectedIndices ?? Array.Empty<IndexPath>();
-            DeselectedItems = deselectedItems ?? Array.Empty<object>();
-            SelectedItems= selectedItems ?? Array.Empty<object>();
+            DeselectedItems = deselectedItems ?? Array.Empty<object?>();
+            SelectedItems= selectedItems ?? Array.Empty<object?>();
         }
 
         /// <summary>
@@ -37,11 +37,11 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets the items that were removed from the selection.
         /// </summary>
-        public IReadOnlyList<object> DeselectedItems { get; }
+        public IReadOnlyList<object?> DeselectedItems { get; }
 
         /// <summary>
         /// Gets the items that were added to the selection.
         /// </summary>
-        public IReadOnlyList<object> SelectedItems { get; }
+        public IReadOnlyList<object?> SelectedItems { get; }
     }
 }