diff --git a/BeWo/View/Detail/Accounting/GkvAbrechnungOverview.xaml.cs b/BeWo/View/Detail/Accounting/GkvAbrechnungOverview.xaml.cs
index 2b416db30..eea96da67 100644
--- a/BeWo/View/Detail/Accounting/GkvAbrechnungOverview.xaml.cs
+++ b/BeWo/View/Detail/Accounting/GkvAbrechnungOverview.xaml.cs
@@ -223,7 +223,7 @@ namespace BeWo.View.Detail.Accounting
 
 		private void Detail_Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
 		{
-			var bewo_window = sender as BeWoWindow;
+			var bewo_window = sender as AnimatedBeWoWindow;
 			var detail_control = bewo_window.GroupBoxContent as GkvAbrechnungDetailControl;
 
 			var vm = detail_control.DataContext as GkvAbrechnungLightVM;