diff --git a/src/Avalonia.Themes.Fluent/Accents/BaseDark.xaml b/src/Avalonia.Themes.Fluent/Accents/BaseDark.xaml
index 89841c92c0..0192fb1b54 100644
--- a/src/Avalonia.Themes.Fluent/Accents/BaseDark.xaml
+++ b/src/Avalonia.Themes.Fluent/Accents/BaseDark.xaml
@@ -36,6 +36,7 @@
     <SolidColorBrush x:Key="SystemControlBackgroundAltMediumHighBrush" Color="{StaticResource SystemAltMediumHighColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundAltMediumBrush" Color="{StaticResource SystemAltMediumColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundAltMediumLowBrush" Color="{StaticResource SystemAltMediumLowColor}" />
+    <SolidColorBrush x:Key="SystemControlBackgroundAltLowBrush" Color="{StaticResource SystemAltLowColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundBaseHighBrush" Color="{StaticResource SystemBaseHighColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundBaseLowBrush" Color="{StaticResource SystemBaseLowColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundBaseMediumBrush" Color="{StaticResource SystemBaseMediumColor}" />
diff --git a/src/Avalonia.Themes.Fluent/Accents/BaseLight.xaml b/src/Avalonia.Themes.Fluent/Accents/BaseLight.xaml
index 89b646fb52..a9e5ed949a 100644
--- a/src/Avalonia.Themes.Fluent/Accents/BaseLight.xaml
+++ b/src/Avalonia.Themes.Fluent/Accents/BaseLight.xaml
@@ -36,6 +36,7 @@
     <SolidColorBrush x:Key="SystemControlBackgroundAltMediumHighBrush" Color="{StaticResource SystemAltMediumHighColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundAltMediumBrush" Color="{StaticResource SystemAltMediumColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundAltMediumLowBrush" Color="{StaticResource SystemAltMediumLowColor}" />
+    <SolidColorBrush x:Key="SystemControlBackgroundAltLowBrush" Color="{StaticResource SystemAltLowColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundBaseHighBrush" Color="{StaticResource SystemBaseHighColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundBaseLowBrush" Color="{StaticResource SystemBaseLowColor}" />
     <SolidColorBrush x:Key="SystemControlBackgroundBaseMediumBrush" Color="{StaticResource SystemBaseMediumColor}" />