diff --git a/shadowsocks-csharp/View/ConfigForm.cs b/shadowsocks-csharp/View/ConfigForm.cs
index d506e8a1..8d2b4781 100755
--- a/shadowsocks-csharp/View/ConfigForm.cs
+++ b/shadowsocks-csharp/View/ConfigForm.cs
@@ -336,13 +336,16 @@ namespace Shadowsocks.View
                 return;
             }
 
-            Server selectedServer = controller.GetCurrentServer();
-            Server clone = (Server)selectedServer.Clone();
+            if (ServersListBox.SelectedIndex >= 0 && ServersListBox.SelectedIndex < _modifiedConfiguration.configs.Count)
+            {
+                Server selectedServer = _modifiedConfiguration.configs[ServersListBox.SelectedIndex];
+                Server clone = (Server)selectedServer.Clone();
 
-            _modifiedConfiguration.configs.Add(clone);
-            LoadConfiguration(_modifiedConfiguration);
-            ServersListBox.SelectedIndex = _modifiedConfiguration.configs.Count - 1;
-            _lastSelectedIndex = ServersListBox.SelectedIndex;
+                _modifiedConfiguration.configs.Add(clone);
+                LoadConfiguration(_modifiedConfiguration);
+                ServersListBox.SelectedIndex = _modifiedConfiguration.configs.Count - 1;
+                _lastSelectedIndex = ServersListBox.SelectedIndex;
+            }
         }
     }
 }