diff --git a/PocketingNT.cpp b/PocketingNT.cpp
index 155a90c..6bd70f5 100644
--- a/PocketingNT.cpp
+++ b/PocketingNT.cpp
@@ -1583,7 +1583,7 @@ PocketingNT::GetExtrusionStm( const ISurfFlatRegion* pSfr, const Vector3d& vtTra
 {
   // controllo dei parametri
    if ( pSfr == nullptr  ||  ! pSfr->IsValid())
-      return false ;
+      return nullptr ;
 
   /*
       pSfr -> superficie da cui estrudere i lati chiusi
@@ -1593,7 +1593,7 @@ PocketingNT::GetExtrusionStm( const ISurfFlatRegion* pSfr, const Vector3d& vtTra
 
    PtrOwner<ISurfFlatRegion> pMySfr( CloneSurfFlatRegion( pSfr)) ;
    if ( IsNull( pMySfr)  ||  ! pMySfr->IsValid())
-      return false ;
+      return nullptr ;
    pMySfr->Translate( vtTrasl) ;
 
   // zuppa di triangoli
diff --git a/SurfRoughing.cpp b/SurfRoughing.cpp
index b63c2f7..38e1f96 100644
--- a/SurfRoughing.cpp
+++ b/SurfRoughing.cpp
@@ -2779,6 +2779,7 @@ SurfRoughing::CloseOpenEdgesUnderTolerance( ISurfFlatRegion* pSfr, double dToler
       }
    }
 
+   RemoveChunksUnderTolerance( pSfrRegular) ;
   // resituisco la superficie
    pSfr->CopyFrom( pSfrRegular) ;
    return true ;