diff --git a/src/Avalonia.Themes.Fluent2/Controls/Window.xaml b/src/Avalonia.Themes.Fluent2/Controls/Window.xaml
index 0113c02e38..72bad357da 100644
--- a/src/Avalonia.Themes.Fluent2/Controls/Window.xaml
+++ b/src/Avalonia.Themes.Fluent2/Controls/Window.xaml
@@ -15,6 +15,13 @@
       <ControlTemplate>
         <Panel>
           <Border Name="PART_TransparencyFallback" IsHitTestVisible="False" />
+          <!-- Default canvas painted via a tree-anchored DynamicResource: styled-setter
+               DynamicResources on TopLevels have failed to resolve in hosted/reopened
+               window scenarios, leaving the white transparency fallback visible.
+               A user-set Background still paints over this via the border above it. -->
+          <Border Name="PART_Fluent2CanvasBackground"
+                  Background="{DynamicResource SolidBackgroundFillColorBaseBrush}"
+                  IsHitTestVisible="False" />
           <Border Background="{TemplateBinding Background}" IsHitTestVisible="False" />
           <Panel Background="Transparent" Margin="{TemplateBinding WindowDecorationMargin}" />
           <VisualLayerManager Name="PART_VisualLayerManager">