diff --git a/MachMgrBasic.cpp b/MachMgrBasic.cpp
index b171887..e34eca2 100644
--- a/MachMgrBasic.cpp
+++ b/MachMgrBasic.cpp
@@ -46,7 +46,7 @@ MachMgr::MachMgr( void)
    m_nMachBaseId = GDB_ID_NULL ;
    m_nMachAuxId = GDB_ID_NULL ;
    m_nCurrMGrpId = GDB_ID_NULL ;
-   m_nCurrMch = 0 ;
+   m_nCurrMch = - 1 ;
    m_nPhasesCount = 0 ;
    m_nCurrPhase = 0 ;
    m_nCurrDispId = GDB_ID_NULL ;
@@ -79,6 +79,7 @@ MachMgr::Clear( void)
          delete m_vMachines.back().pMachine ;
       m_vMachines.pop_back() ;
    }
+   m_nCurrMch = - 1 ;
 }
 
 //----------------------------------------------------------------------------
diff --git a/MachMgrMachines.cpp b/MachMgrMachines.cpp
index f3a4b72..7fd0a0d 100644
--- a/MachMgrMachines.cpp
+++ b/MachMgrMachines.cpp
@@ -84,7 +84,7 @@ MachMgr::SetCurrMachine( const string& sMachineName)
       return false ;
   // verifica ed eventuale caricamento della macchina
    if ( ! LoadMachine( sMachineName))
-      return GDB_ID_NULL ;
+      return false ;
   // imposto i dati della macchina corrente
    m_nCurrMch = GetMachine( sMachineName) ;
   // nascondo la macchina