diff --git a/GdbGroup.cpp b/GdbGroup.cpp
index c0c2108..0668ac8 100644
--- a/GdbGroup.cpp
+++ b/GdbGroup.cpp
@@ -116,8 +116,11 @@ GdbGroup::Save( NgeWriter& ngeOut) const
    if ( ! GdbObj::SaveAttribs( ngeOut))
       bOk = false ;
 
-  // dati del riferimento
+  // dati geometrici
    ngeOut.WriteKey( NGE_G) ;
+   // puntatore alla prima copia (per ora NULL)
+   ngeOut.WriteInt( GDB_ID_NULL, nullptr, true) ;
+   // frame
    if ( ! m_gfrFrame.Save( ngeOut))
       bOk = false ;
 
@@ -160,6 +163,11 @@ GdbGroup::Load( int nNgeId, NgeReader& ngeIn, int& nParentId)
    if ( nKey != NGE_G)
       return false ;
 
+  // leggo il puntatore alla prima copia
+   int nCopyId ;
+   if ( ! ngeIn.ReadInt( nCopyId, nullptr, true))
+      return false ;
+
   // leggo i dati del riferimento
    return m_gfrFrame.Load( ngeIn) ;
 }