diff --git a/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/ThemeManager.cs b/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/ThemeManager.cs
index a70940d98de..852f7920388 100644
--- a/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/ThemeManager.cs
+++ b/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/ThemeManager.cs
@@ -182,6 +182,16 @@ internal static void SyncDeferredThemeModeAndResources()
 
     internal static void SyncWindowThemeModeAndResources(Window window)
     {
+
+        if(window._deferThemeLoading)
+        {
+            IgnoreWindowResourcesChange = true;
+            var uri = GetThemeResource(window.ThemeMode);
+            window.Resources.MergedDictionaries.Insert(0, new ResourceDictionary() { Source = uri });
+            window._deferThemeLoading = false;
+            IgnoreWindowResourcesChange = false;
+        }
+
         ThemeMode themeMode = GetThemeModeFromResourceDictionary(window.Resources);
 
         if(window.ThemeMode != themeMode)
diff --git a/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs b/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs
index c4b88361334..71f21ef5e1c 100644
--- a/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs
+++ b/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs
@@ -2573,7 +2573,7 @@ internal void CreateSourceWindow(bool duringShow)
                     }
                 }
 
-                if(_deferThemeLoading)
+                if(_deferThemeLoading || ThemeMode != ThemeMode.None)
                 {
                     _deferThemeLoading = false;
                     ThemeManager.OnWindowThemeChanged(this, ThemeMode.None, ThemeMode);