diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ResourceInclude.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ResourceInclude.cs
index ce9e3fd4b1..1627053e67 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ResourceInclude.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ResourceInclude.cs
@@ -22,7 +22,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
         {
             get
             {
-                if (_loaded is null)
+                if (_loaded == null)
                 {
                     _isLoading = true;
                     var loader = new AvaloniaXamlLoader();
diff --git a/src/Markup/Avalonia.Markup.Xaml/Styling/StyleInclude.cs b/src/Markup/Avalonia.Markup.Xaml/Styling/StyleInclude.cs
index 9d5b56ebb4..ea9042f779 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Styling/StyleInclude.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/Styling/StyleInclude.cs
@@ -48,7 +48,7 @@ namespace Avalonia.Markup.Xaml.Styling
         {
             get
             {
-                if (_loaded is null)
+                if (_loaded == null)
                 {
                     _isLoading = true;
                     var loader = new AvaloniaXamlLoader();