diff --git a/src/Application.vala b/src/Application.vala
index 95b2bd9..938a4b3 100644
--- a/src/Application.vala
+++ b/src/Application.vala
@@ -54,19 +54,10 @@ public class MyApp : Gtk.Application {
 
         settings.bind ("window-maximized", main_window, "maximized", SettingsBindFlags.SET);
 
-        // Use Css
-        var provider = new Gtk.CssProvider ();
-        provider.load_from_resource ("/io/github/yourusername/yourrepositoryname/Application.css");
-
-        Gtk.StyleContext.add_provider_for_display (
-            Gdk.Display.get_default (),
-            provider, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION
-        );
-
         main_window.present ();
     }
 
     public static int main (string[] args) {
         return new MyApp ().run (args);
     }
-}
\ No newline at end of file
+}
diff --git a/src/MainWindow.vala b/src/MainWindow.vala
index 1081aa2..5d2a9aa 100644
--- a/src/MainWindow.vala
+++ b/src/MainWindow.vala
@@ -20,6 +20,10 @@ public class MainWindow : Gtk.ApplicationWindow {
     }
 
     construct {
+        var provider = new Gtk.CssProvider ();
+        provider.load_from_resource ("/io/github/yourusername/yourrepositoryname/Application.css");
+        add_css_class (provider.to_string());
+
         var start_header = new Gtk.HeaderBar () {
             show_title_buttons = false,
             title_widget = new Gtk.Label ("")
@@ -64,4 +68,4 @@ public class MainWindow : Gtk.ApplicationWindow {
             gtk_settings.gtk_theme_name = "io.elementary.stylesheet.blueberry";
         }
     }
-}
\ No newline at end of file
+}