diff --git a/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/HC.xaml b/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/HC.xaml
index 48a447170..b695a7d90 100644
--- a/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/HC.xaml
+++ b/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Resources/Theme/HC.xaml
@@ -83,7 +83,6 @@
 
     <SolidColorBrush x:Key="ControlSolidFillColorDefaultBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
 
-    <SolidColorBrush x:Key="SystemColorWindowColorBrush" Color="Transparent" />
     <SolidColorBrush x:Key="SubtleFillColorSecondaryBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
     <SolidColorBrush x:Key="SubtleFillColorTertiaryBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
     <SolidColorBrush x:Key="SubtleFillColorDisabledBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
@@ -636,7 +635,6 @@
 
     <Color x:Key="ControlSolidFillColorDefault">#2D3236</Color>
 
-    <Color x:Key="SystemColorWindowColor">Transparent</Color>
     <Color x:Key="SubtleFillColorSecondary">#2D3236</Color>
     <Color x:Key="SubtleFillColorTertiary">#2D3236</Color>
     <Color x:Key="SubtleFillColorDisabled">#2D3236</Color>
diff --git a/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.HC.xaml b/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.HC.xaml
index 843bde173..504e543e6 100644
--- a/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.HC.xaml
+++ b/src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.HC.xaml
@@ -138,7 +138,6 @@
   <SolidColorBrush x:Key="ControlStrongFillColorDefaultBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
   <SolidColorBrush x:Key="ControlStrongFillColorDisabledBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
   <SolidColorBrush x:Key="ControlSolidFillColorDefaultBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
-  <SolidColorBrush x:Key="SystemColorWindowColorBrush" Color="Transparent" />
   <SolidColorBrush x:Key="SubtleFillColorSecondaryBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
   <SolidColorBrush x:Key="SubtleFillColorTertiaryBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
   <SolidColorBrush x:Key="SubtleFillColorDisabledBrush" Color="{StaticResource SystemColorButtonFaceColor}" />
@@ -612,7 +611,6 @@
   <Color x:Key="ControlStrongFillColorDefault">#2D3236</Color>
   <Color x:Key="ControlStrongFillColorDisabled">#2D3236</Color>
   <Color x:Key="ControlSolidFillColorDefault">#2D3236</Color>
-  <Color x:Key="SystemColorWindowColor">Transparent</Color>
   <Color x:Key="SubtleFillColorSecondary">#2D3236</Color>
   <Color x:Key="SubtleFillColorTertiary">#2D3236</Color>
   <Color x:Key="SubtleFillColorDisabled">#2D3236</Color>