diff --git a/SceneSelect.cpp b/SceneSelect.cpp
index edf3f3d..c64471b 100644
--- a/SceneSelect.cpp
+++ b/SceneSelect.cpp
@@ -189,6 +189,9 @@ Scene::UnselectableAdd( int nId)
   // non si ammettono radice e id negativi
    if ( nId <= GDB_ID_ROOT)
       return false ;
+  // verifico se già presente
+   if ( binary_search( m_Unsel.begin(), m_Unsel.end(), nId))
+      return true ;
   // inserisco l'elemento
    m_Unsel.push_back( nId) ;
   // ordino in senso crescente