diff --git a/src/Wpf.Ui/UiApplication.cs b/src/Wpf.Ui/UiApplication.cs
index c15da0135..36ebb1c6c 100644
--- a/src/Wpf.Ui/UiApplication.cs
+++ b/src/Wpf.Ui/UiApplication.cs
@@ -137,14 +137,7 @@ public void Shutdown()
 
     private static bool ApplicationHasResources(Application application)
     {
-        return application
-            .Resources.MergedDictionaries.Where(e => e.Source is not null)
-            .Any(e =>
-                e.Source.ToString()
-                    .Contains(
-                        Appearance.ApplicationThemeManager.LibraryNamespace,
-                        StringComparison.OrdinalIgnoreCase
-                    )
-            );
+        return application.Resources.MergedDictionaries.Any(e => e.Source?.ToString()
+                                                                  .Contains(Appearance.ApplicationThemeManager.LibraryNamespace, StringComparison.OrdinalIgnoreCase) == true);
     }
 }