diff --git a/gtk/apport-gtk b/gtk/apport-gtk
index 5e9c3b1c4..ab2b97032 100755
--- a/gtk/apport-gtk
+++ b/gtk/apport-gtk
@@ -632,7 +632,7 @@ class GTKUserInterface(apport.ui.UserInterface):
         return True
 
     def on_progress_window_close_event(
-        self, widget: Gtk.Widget, event: Gdk.Event
+        self, widget: Gtk.Widget, event: Gdk.Event | None = None
     ) -> None:
         # pylint: disable=unused-argument
         self.w("window_information_collection").hide()