diff --git a/v2rayN/v2rayN/Common/JsonUtils.cs b/v2rayN/v2rayN/Common/JsonUtils.cs
index 2198ba35..ab81d41e 100644
--- a/v2rayN/v2rayN/Common/JsonUtils.cs
+++ b/v2rayN/v2rayN/Common/JsonUtils.cs
@@ -105,9 +105,12 @@ namespace v2rayN
         /// <param name="filePath"></param>
         /// <param name="nullValue"></param>
         /// <returns></returns>
-        public static int ToFile(object? obj, string filePath, bool nullValue = true)
+        public static int ToFile(object? obj, string? filePath, bool nullValue = true)
         {
-            int result;
+            if (filePath is null)
+            {
+                return -1;
+            }
             try
             {
                 using FileStream file = File.Create(filePath);
@@ -119,14 +122,13 @@ namespace v2rayN
                 };
 
                 JsonSerializer.Serialize(file, obj, options);
-                result = 0;
+                return 0;
             }
             catch (Exception ex)
             {
                 Logging.SaveLog(ex.Message, ex);
-                result = -1;
+                return -1;
             }
-            return result;
         }
     }
 }
\ No newline at end of file
diff --git a/v2rayN/v2rayN/Handler/CoreConfigSingbox.cs b/v2rayN/v2rayN/Handler/CoreConfigSingbox.cs
index c2cd926c..1fc6858c 100644
--- a/v2rayN/v2rayN/Handler/CoreConfigSingbox.cs
+++ b/v2rayN/v2rayN/Handler/CoreConfigSingbox.cs
@@ -25,6 +25,11 @@ namespace v2rayN.Handler
                     msg = ResUI.CheckServerSettings;
                     return -1;
                 }
+                if (node.GetNetwork() == nameof(ETransport.kcp))
+                {
+                    msg = ResUI.Incorrectconfiguration + $" - {node.GetNetwork()}";
+                    return -1;
+                }
 
                 msg = ResUI.InitialConfiguration;
 
diff --git a/v2rayN/v2rayN/Handler/CoreHandler.cs b/v2rayN/v2rayN/Handler/CoreHandler.cs
index b6b37c2f..05a8e08b 100644
--- a/v2rayN/v2rayN/Handler/CoreHandler.cs
+++ b/v2rayN/v2rayN/Handler/CoreHandler.cs
@@ -38,7 +38,8 @@ namespace v2rayN.Handler
             string fileName = Utils.GetConfigPath(Global.CoreConfigFileName);
             if (CoreConfigHandler.GenerateClientConfig(node, fileName, out string msg, out string content) != 0)
             {
-                ShowMsg(false, msg);
+                ShowMsg(false, msg); 
+                return;
             }
             else
             {