diff --git a/v2rayN/v2rayN/Views/MainWindow.xaml b/v2rayN/v2rayN/Views/MainWindow.xaml
index 2e63d3fd..3511a429 100644
--- a/v2rayN/v2rayN/Views/MainWindow.xaml
+++ b/v2rayN/v2rayN/Views/MainWindow.xaml
@@ -289,6 +289,7 @@
                         </Menu>
 
                         <materialDesign:PopupBox
+                            x:Name="themePopupBox"
                             Padding="-2"
                             HorizontalAlignment="Right"
                             StaysOpen="True"