diff --git a/samples/VirtualizationDemo/App.xaml b/samples/VirtualizationDemo/App.xaml
index 0b64d0c09b..eb5f0e4dca 100644
--- a/samples/VirtualizationDemo/App.xaml
+++ b/samples/VirtualizationDemo/App.xaml
@@ -1,9 +1,7 @@
-<Application
-    xmlns="https://github.com/avaloniaui" 
-    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    x:Class="VirtualizationDemo.App">
-    <Application.Styles>
-        <StyleInclude Source="avares://Avalonia.Themes.Simple/DefaultTheme.xaml"/>
-        <StyleInclude Source="avares://Avalonia.Themes.Simple/Accents/BaseLight.xaml"/>
-    </Application.Styles>
-</Application>
\ No newline at end of file
+<Application xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             x:Class="VirtualizationDemo.App">
+  <Application.Styles>
+    <SimpleTheme />
+  </Application.Styles>
+</Application>
diff --git a/tests/Avalonia.Benchmarks/Themes/ThemeBenchmark.cs b/tests/Avalonia.Benchmarks/Themes/ThemeBenchmark.cs
index c64931a6ef..aed8a38d08 100644
--- a/tests/Avalonia.Benchmarks/Themes/ThemeBenchmark.cs
+++ b/tests/Avalonia.Benchmarks/Themes/ThemeBenchmark.cs
@@ -4,6 +4,8 @@ using Avalonia.Controls;
 using Avalonia.Markup.Xaml.Styling;
 using Avalonia.Platform;
 using Avalonia.Styling;
+using Avalonia.Themes.Fluent;
+using Avalonia.Themes.Simple;
 using Avalonia.UnitTests;
 
 using BenchmarkDotNet.Attributes;
@@ -25,32 +27,25 @@ namespace Avalonia.Benchmarks.Themes
         }
 
         [Benchmark]
-        [Arguments("avares://Avalonia.Themes.Fluent/FluentDark.xaml")]
-        [Arguments("avares://Avalonia.Themes.Fluent/FluentLight.xaml")]
-        public bool InitFluentTheme(string themeUri)
+        [Arguments(FluentThemeMode.Dark)]
+        [Arguments(FluentThemeMode.Light)]
+        public bool InitFluentTheme(FluentThemeMode mode)
         {
-            UnitTestApplication.Current.Styles[0] = new StyleInclude(new Uri("resm:Styles?assembly=Avalonia.Benchmarks"))
+            UnitTestApplication.Current.Styles[0] = new FluentTheme(new Uri("resm:Styles?assembly=Avalonia.Benchmarks"))
             {
-                Source = new Uri(themeUri)
+                Mode = mode
             };
             return ((IResourceHost)UnitTestApplication.Current).TryGetResource("SystemAccentColor", out _);
         }
 
         [Benchmark]
-        [Arguments("avares://Avalonia.Themes.Simple/Accents/BaseLight.xaml")]
-        [Arguments("avares://Avalonia.Themes.Simple/Accents/BaseDark.xaml")]
-        public bool InitDefaultTheme(string themeUri)
+        [Arguments(SimpleThemeMode.Dark)]
+        [Arguments(SimpleThemeMode.Light)]
+        public bool InitDefaultTheme(SimpleThemeMode mode)
         {
-            UnitTestApplication.Current.Styles[0] = new Styles
+            UnitTestApplication.Current.Styles[0] = new SimpleTheme(new Uri("resm:Styles?assembly=Avalonia.Benchmarks"))
             {
-                new StyleInclude(new Uri("resm:Styles?assembly=Avalonia.Benchmarks"))
-                {
-                    Source = new Uri(themeUri)
-                },
-                new StyleInclude(new Uri("resm:Styles?assembly=Avalonia.Benchmarks"))
-                {
-                    Source = new Uri("avares://Avalonia.Themes.Simple/DefaultTheme.xaml")
-                }
+                Mode = mode
             };
             return ((IResourceHost)UnitTestApplication.Current).TryGetResource("ThemeAccentColor", out _);
         }
diff --git a/tests/Avalonia.DesignerSupport.TestApp/App.xaml b/tests/Avalonia.DesignerSupport.TestApp/App.xaml
index 803cae09c8..ad32431b37 100644
--- a/tests/Avalonia.DesignerSupport.TestApp/App.xaml
+++ b/tests/Avalonia.DesignerSupport.TestApp/App.xaml
@@ -1,10 +1,7 @@
-<Application
-    x:Class="Avalonia.DesignerSupport.TestApp.App"
-    xmlns="https://github.com/avaloniaui"
-    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
-    <Application.Styles>
-        <StyleInclude Source="avares://Avalonia.Themes.Simple/DefaultTheme.xaml" />
-        <StyleInclude Source="avares://Avalonia.Themes.Simple/Accents/Base.xaml" />
-        <StyleInclude Source="avares://Avalonia.Themes.Simple/Accents/BaseLight.xaml" />
-    </Application.Styles>
+<Application x:Class="Avalonia.DesignerSupport.TestApp.App"
+             xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  <Application.Styles>
+    <SimpleTheme />
+  </Application.Styles>
 </Application>