diff --git a/BtlGeomProc.cpp b/BtlGeomProc.cpp
index 2f57f12..67cc25f 100644
--- a/BtlGeomProc.cpp
+++ b/BtlGeomProc.cpp
@@ -3774,7 +3774,7 @@ BtlGeom::AddStepJointNotch( int nGroup, int nProc, int nSide, const string& sDes
    if ( dStartY < 0)
       pCrv->Translate( - dStartY * frSide.VersY()) ;
    pCrv->SetExtrusion( frSide.VersY()) ;
-   double dThick = min( dWidth + min( 0., dStartY), GetSideWidth( nSide)) ;
+   double dThick = min( dWidth + min( 0., dStartY), GetSideWidth( nSide)- max( 0., dStartY)) ;
    pCrv->SetThickness( dThick) ;
   // inserisco la curva nel DB geometrico
    int nTId = m_pGDB->AddGeoObj( GDB_ID_NULL, m_nProcsId, Release( pCrv)) ;