diff --git a/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION.cs b/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION.cs
index 351aa1ca..7a2dbe15 100644
--- a/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION.cs
+++ b/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION.cs
@@ -76,7 +76,7 @@ namespace Shadowsocks.Util.SystemProxy
     /// The StructLayout and FieldOffset attributes could help to decrease the struct size.
     /// </summary>
     [StructLayout(LayoutKind.Explicit)]
-    public struct INTERNET_PER_CONN_OPTION_OptionUnion
+    public struct INTERNET_PER_CONN_OPTION_OptionUnion : IDisposable
     {
         // A value in INTERNET_OPTION_PER_CONN_FLAGS.
         [FieldOffset(0)]
@@ -85,6 +85,24 @@ namespace Shadowsocks.Util.SystemProxy
         public System.IntPtr pszValue;
         [FieldOffset(0)]
         public System.Runtime.InteropServices.ComTypes.FILETIME ftValue;
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        private void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                if (pszValue != IntPtr.Zero)
+                {
+                    Marshal.FreeHGlobal(pszValue);
+                    pszValue = IntPtr.Zero;
+                }
+            }
+        }
     }
 
     [StructLayout(LayoutKind.Sequential)]
diff --git a/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION_LIST.cs b/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION_LIST.cs
index b15870ce..601cde38 100644
--- a/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION_LIST.cs
+++ b/shadowsocks-csharp/Util/SystemProxy/INTERNET_PER_CONN_OPTION_LIST.cs
@@ -17,22 +17,47 @@
  WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
 \***************************************************************************/
 
+using System;
 using System.Runtime.InteropServices;
 
 namespace Shadowsocks.Util.SystemProxy
 {
     [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
-    public struct INTERNET_PER_CONN_OPTION_LIST
+    public struct INTERNET_PER_CONN_OPTION_LIST : IDisposable
     {
         public int Size;
 
         // The connection to be set. NULL means LAN.
         public System.IntPtr Connection;
-        
+
         public int OptionCount;
         public int OptionError;
 
         // List of INTERNET_PER_CONN_OPTIONs.
         public System.IntPtr pOptions;
+
+        public void Dispose()
+        {
+            Dispose( true );
+            GC.SuppressFinalize( this );
+        }
+
+        private void Dispose( bool disposing )
+        {
+            if ( disposing )
+            {
+                if ( Connection != IntPtr.Zero )
+                {
+                    Marshal.FreeHGlobal( Connection );
+                    Connection = IntPtr.Zero;
+                }
+
+                if ( pOptions != IntPtr.Zero )
+                {
+                    Marshal.FreeHGlobal( pOptions );
+                    pOptions = IntPtr.Zero;
+                }
+            }
+        }
     }
 }
diff --git a/shadowsocks-csharp/Util/SystemProxy/WinINet.cs b/shadowsocks-csharp/Util/SystemProxy/WinINet.cs
index a1de566c..a95a3b5d 100644
--- a/shadowsocks-csharp/Util/SystemProxy/WinINet.cs
+++ b/shadowsocks-csharp/Util/SystemProxy/WinINet.cs
@@ -121,12 +121,6 @@ namespace Shadowsocks.Util.SystemProxy
                 intptrStruct, optionListSize);
 
             // Free the allocated memory.
-            foreach (var v in _optionlist)
-            {
-                // free strings
-                if (v.Value.pszValue != IntPtr.Zero)
-                    Marshal.FreeHGlobal(v.Value.pszValue);
-            }
             Marshal.FreeCoTaskMem(buffer);
             Marshal.FreeCoTaskMem(intptrStruct);