diff --git a/ExportDxf.cpp b/ExportDxf.cpp
index 6d5efb3..de5326c 100644
--- a/ExportDxf.cpp
+++ b/ExportDxf.cpp
@@ -1198,7 +1198,7 @@ ExportDxf::WriteCurve3d( const string& sLay, int nCol, const ICurve* pCrv, const
       return false ;
   // trasformo in polilinea
    PolyLine PL ;
-   if ( ! pCrv->ApproxWithLines( BEZ_LIN_APPROX, BEZ_ANG_APPROX_DEG, PL))
+   if ( ! pCrv->ApproxWithLines( BEZ_LIN_APPROX, BEZ_ANG_APPROX_DEG, ICurve::APL_STD, PL))
       return false ;
   // recupero lo spessore
    double dThick = 0 ;