diff --git a/SurfBezier.cpp b/SurfBezier.cpp
index 14d92b3..4ae0115 100644
--- a/SurfBezier.cpp
+++ b/SurfBezier.cpp
@@ -1124,7 +1124,7 @@ bool
 SurfBezier::GetBBox( const Frame3d& frRef, BBox3d& b3Ref, int nFlag) const
 {
    // basta approssimato
-   if ( ( nFlag & BBF_EXACT) == 0) {
+   if ( ( nFlag & BBF_EXACT) == 0  &&  ! m_bTrimmed) {
       for ( int i = 0 ; i < GetDim() ; ++ i) {
          Point3d ptTemp = m_vPtCtrl[i] ;
          ptTemp.ToGlob( frRef) ;