diff --git a/v2rayN/v2rayN/ViewModels/MainWindowViewModel.cs b/v2rayN/v2rayN/ViewModels/MainWindowViewModel.cs
index a7006a7d..14bb5674 100644
--- a/v2rayN/v2rayN/ViewModels/MainWindowViewModel.cs
+++ b/v2rayN/v2rayN/ViewModels/MainWindowViewModel.cs
@@ -3,6 +3,7 @@ using DynamicData.Binding;
 using MaterialDesignColors;
 using MaterialDesignColors.ColorManipulation;
 using MaterialDesignThemes.Wpf;
+using MahApps.Metro;
 using ReactiveUI;
 using ReactiveUI.Fody.Helpers;
 using Splat;