diff --git a/src/dotnet/FileSystem.cs b/src/dotnet/FileSystem.cs
index dff4662d..7730c1ed 100644
--- a/src/dotnet/FileSystem.cs
+++ b/src/dotnet/FileSystem.cs
@@ -286,7 +286,7 @@ namespace Fsp
             UInt32 FileAttributes,
             IntPtr SecurityDescriptor,
             UInt64 AllocationSize,
-            out FullContext FullContext,
+            ref FullContext FullContext,
             out FileInfo FileInfo)
         {
             FileSystem self = (FileSystem)Api.FspFileSystemGetUserContext(FileSystem);
@@ -304,7 +304,7 @@ namespace Fsp
                     out FileNode,
                     out FileDesc,
                     out FileInfo);
-                Api.SetFullContext(out FullContext, FileNode, FileDesc);
+                Api.SetFullContext(ref FullContext, FileNode, FileDesc);
                 return Result;
             }
             catch (Exception ex)
@@ -319,7 +319,7 @@ namespace Fsp
             String FileName,
             UInt32 CreateOptions,
             UInt32 GrantedAccess,
-            out FullContext FullContext,
+            ref FullContext FullContext,
             out FileInfo FileInfo)
         {
             FullContext = default(FullContext);
diff --git a/src/dotnet/Interop.cs b/src/dotnet/Interop.cs
index a2a1e2ee..04f81693 100644
--- a/src/dotnet/Interop.cs
+++ b/src/dotnet/Interop.cs
@@ -202,7 +202,7 @@ namespace Fsp.Interop
                 UInt32 FileAttributes,
                 IntPtr SecurityDescriptor,
                 UInt64 AllocationSize,
-                out FullContext FullContext,
+                ref FullContext FullContext,
                 out FileInfo FileInfo);
             [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
             internal delegate Int32 Open(
@@ -210,7 +210,7 @@ namespace Fsp.Interop
                 [MarshalAs(UnmanagedType.LPWStr)] String FileName,
                 UInt32 CreateOptions,
                 UInt32 GrantedAccess,
-                out FullContext FullContext,
+                ref FullContext FullContext,
                 out FileInfo FileInfo);
             [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
             internal delegate Int32 Overwrite(
@@ -469,13 +469,42 @@ namespace Fsp.Interop
         internal static void GetFullContext(ref FullContext FullContext,
             out Object FileNode, out Object FileDesc)
         {
-            FileNode = default(Object);
-            FileDesc = default(Object);
+            FileNode = 0 != FullContext.UserContext ?
+                ((GCHandle)(IntPtr)FullContext.UserContext).Target : null;
+            FileDesc = 0 != FullContext.UserContext2 ?
+                ((GCHandle)(IntPtr)FullContext.UserContext2).Target : null;
         }
-        internal static void SetFullContext(out FullContext FullContext,
+        internal static void SetFullContext(ref FullContext FullContext,
             Object FileNode, Object FileDesc)
         {
-            FullContext = default(FullContext);
+            if (null != FileNode)
+            {
+                Debug.Assert(0 == FullContext.UserContext);
+                GCHandle Handle = GCHandle.Alloc(FileNode, GCHandleType.Normal);
+                FullContext.UserContext = (UInt64)(IntPtr)Handle;
+            }
+            else
+            {
+                if (0 != FullContext.UserContext)
+                {
+                    ((GCHandle)(IntPtr)FullContext.UserContext).Free();
+                    FullContext.UserContext = 0;
+                }
+            }
+            if (null != FileDesc)
+            {
+                Debug.Assert(0 == FullContext.UserContext2);
+                GCHandle Handle = GCHandle.Alloc(FileDesc, GCHandleType.Normal);
+                FullContext.UserContext2 = (UInt64)(IntPtr)Handle;
+            }
+            else
+            {
+                if (0 != FullContext.UserContext2)
+                {
+                    ((GCHandle)(IntPtr)FullContext.UserContext2).Free();
+                    FullContext.UserContext2 = 0;
+                }
+            }
         }
 
         [DllImport("advapi32.dll", CallingConvention = CallingConvention.StdCall)]