diff --git a/shadowsocks-csharp/Controller/System/SystemProxy.cs b/shadowsocks-csharp/Controller/System/SystemProxy.cs
index b932b240..b06b00c6 100644
--- a/shadowsocks-csharp/Controller/System/SystemProxy.cs
+++ b/shadowsocks-csharp/Controller/System/SystemProxy.cs
@@ -21,25 +21,32 @@ namespace Shadowsocks.Controller
                 enabled = false;
             }
 
-            if (enabled)
+            try
             {
-                if (global)
+                if (enabled)
                 {
-                    WinINet.SetIEProxy(true, true, "127.0.0.1:" + config.localPort.ToString(), "");
+                    if (global)
+                    {
+                        WinINet.SetIEProxy(true, true, "127.0.0.1:" + config.localPort.ToString(), "");
+                    }
+                    else
+                    {
+                        string pacUrl;
+                        if (config.useOnlinePac && !config.pacUrl.IsNullOrEmpty())
+                            pacUrl = config.pacUrl;
+                        else
+                            pacUrl = $"http://127.0.0.1:{config.localPort}/pac?t={GetTimestamp(DateTime.Now)}";
+                        WinINet.SetIEProxy(true, false, "", pacUrl);
+                    }
                 }
                 else
                 {
-                    string pacUrl;
-                    if (config.useOnlinePac && !config.pacUrl.IsNullOrEmpty())
-                        pacUrl = config.pacUrl;
-                    else
-                        pacUrl = $"http://127.0.0.1:{config.localPort}/pac?t={GetTimestamp(DateTime.Now)}";
-                    WinINet.SetIEProxy(true, false, "", pacUrl);
+                    WinINet.SetIEProxy(false, false, "", "");
                 }
             }
-            else
+            catch (ProxyException ex)
             {
-                WinINet.SetIEProxy(false, false, "", "");
+                Logging.LogUsefulException(ex);
             }
         }
     }
diff --git a/shadowsocks-csharp/Util/SystemProxy/ProxyException.cs b/shadowsocks-csharp/Util/SystemProxy/ProxyException.cs
new file mode 100644
index 00000000..67a00e2c
--- /dev/null
+++ b/shadowsocks-csharp/Util/SystemProxy/ProxyException.cs
@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Shadowsocks.Util.SystemProxy
+{
+    class ProxyException : Exception
+    {
+        public ProxyException()
+        {
+        }
+
+        public ProxyException(string message) : base(message)
+        {
+        }
+
+        public ProxyException(string message, Exception innerException) : base(message, innerException)
+        {
+        }
+
+        protected ProxyException(SerializationInfo info, StreamingContext context) : base(info, context)
+        {
+        }
+    }
+}
diff --git a/shadowsocks-csharp/Util/SystemProxy/WinINet.cs b/shadowsocks-csharp/Util/SystemProxy/WinINet.cs
index c5dddee9..184f47e7 100644
--- a/shadowsocks-csharp/Util/SystemProxy/WinINet.cs
+++ b/shadowsocks-csharp/Util/SystemProxy/WinINet.cs
@@ -17,6 +17,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using System.Runtime.InteropServices;
 using Shadowsocks.Controller;
@@ -131,7 +132,7 @@ namespace Shadowsocks.Util.SystemProxy
             // Throw an exception if this operation failed.
             if (!bReturn)
             {
-                throw new Exception("InternetSetOption: " + Marshal.GetLastWin32Error());
+                throw new ProxyException("InternetSetOption failed.", new Win32Exception());
             }
 
             // Notify the system that the registry settings have been changed and cause
@@ -161,7 +162,7 @@ namespace Shadowsocks.Util.SystemProxy
             var ret = RemoteAccessService.GetAllConns(ref allConnections);
 
             if (ret == 2)
-                throw new Exception("Cannot get all connections");
+                throw new ProxyException("Cannot get all connections");
 
             if (ret == 1)
             {
diff --git a/shadowsocks-csharp/shadowsocks-csharp.csproj b/shadowsocks-csharp/shadowsocks-csharp.csproj
index 26ea4fd2..d1881c87 100644
--- a/shadowsocks-csharp/shadowsocks-csharp.csproj
+++ b/shadowsocks-csharp/shadowsocks-csharp.csproj
@@ -191,6 +191,7 @@
     <Compile Include="Util\SystemProxy\INTERNET_PER_CONN_OPTION.cs" />
     <Compile Include="Util\SystemProxy\INTERNET_PER_CONN_OPTION_LIST.cs" />
     <Compile Include="Util\SystemProxy\NativeMethods.cs" />
+    <Compile Include="Util\SystemProxy\ProxyException.cs" />
     <Compile Include="Util\SystemProxy\RAS.cs" />
     <Compile Include="Util\SystemProxy\WinINet.cs" />
     <Compile Include="Util\Util.cs" />