Index: win_iocp_handle_service.ipp
===================================================================
--- win_iocp_handle_service.ipp	(revision 85729)
+++ win_iocp_handle_service.ipp	(working copy)
@@ -366,18 +366,17 @@
   }
   else
   {
-    DWORD bytes_transferred = 0;
     op->Offset = offset & 0xFFFFFFFF;
     op->OffsetHigh = (offset >> 32) & 0xFFFFFFFF;
     BOOL ok = ::WriteFile(impl.handle_,
         boost::asio::buffer_cast<LPCVOID>(buffer),
         static_cast<DWORD>(boost::asio::buffer_size(buffer)),
-        &bytes_transferred, op);
+        NULL, op);
     DWORD last_error = ::GetLastError();
     if (!ok && last_error != ERROR_IO_PENDING
         && last_error != ERROR_MORE_DATA)
     {
-      iocp_service_.on_completion(op, last_error, bytes_transferred);
+      iocp_service_.on_completion(op, last_error, 0);
     }
     else
     {
@@ -474,18 +473,17 @@
   }
   else
   {
-    DWORD bytes_transferred = 0;
     op->Offset = offset & 0xFFFFFFFF;
     op->OffsetHigh = (offset >> 32) & 0xFFFFFFFF;
     BOOL ok = ::ReadFile(impl.handle_,
         boost::asio::buffer_cast<LPVOID>(buffer),
         static_cast<DWORD>(boost::asio::buffer_size(buffer)),
-        &bytes_transferred, op);
+        NULL, op);
     DWORD last_error = ::GetLastError();
     if (!ok && last_error != ERROR_IO_PENDING
         && last_error != ERROR_MORE_DATA)
     {
-      iocp_service_.on_completion(op, last_error, bytes_transferred);
+      iocp_service_.on_completion(op, last_error, 0);
     }
     else
     {