diff --git a/EXE_GdbModifyCurve.cpp b/EXE_GdbModifyCurve.cpp
index 1e29a5e..0734d53 100644
--- a/EXE_GdbModifyCurve.cpp
+++ b/EXE_GdbModifyCurve.cpp
@@ -100,7 +100,7 @@ ExeOffsetCurveAdv( int nId, double dDist, int nType, int* pnCount)
    IGeomDB* pGeomDB = GetCurrGeomDB() ;
    VERIFY_GEOMDB( pGeomDB, GDB_ID_NULL)
   // recupero la curva
-   ICurve* pCurve = GetCurve( pGeomDB->GetGeoObj( nId)) ;
+   const ICurve* pCurve = GetCurve( pGeomDB->GetGeoObj( nId)) ;
   // eseguo l'offset
    OffsetCurve OffsCrv ;
    bool bOk = OffsCrv.Make( pCurve, dDist, nType) ;