diff --git a/SurfTriMesh.cpp b/SurfTriMesh.cpp
index 3699847..12a7bac 100644
--- a/SurfTriMesh.cpp
+++ b/SurfTriMesh.cpp
@@ -3710,6 +3710,8 @@ SurfTriMesh::SetTFlag( int nId, int nTFlag)
    if ( nId < 0  ||  nId >= GetTriangleSize()  ||  m_vTria[nId].nIdVert[0] == SVT_DEL)
       return false ;
    m_vTria[nId].nTFlag = nTFlag ;
+   m_nMaxTFlag = max( m_nMaxTFlag, abs( nTFlag)) ;
+   m_OGrMgr.Clear() ;
    return true ;
 }
 
diff --git a/SurfTriMesh.h b/SurfTriMesh.h
index c6c732b..fe80811 100644
--- a/SurfTriMesh.h
+++ b/SurfTriMesh.h
@@ -318,6 +318,8 @@ class SurfTriMesh : public ISurfTriMesh, public IGeoObjRW
       int GetPartCount( void) const override ;
       bool RemovePart( int nPart) override ;
       SurfTriMesh* ClonePart( int nPart) const override ;
+      bool SetTFlag( int nId, int nTFlag) override ;
+      bool GetTFlag( int nId, int& nFlag) const override ;
       int  GetMaxTFlag( void) const override 
               { return m_nMaxTFlag ; }
       bool ResetTFlags( void) override ;
@@ -343,10 +345,8 @@ class SurfTriMesh : public ISurfTriMesh, public IGeoObjRW
       bool ExistsTriangle( int nT) const
               { return ( nT >= 0  &&  nT < GetTriangleSize()  &&  m_vTria[nT].nIdVert[0] != SVT_DEL) ; }
       bool GetTriangleAdjacencies( int nId, int nIdAdjTriaId[3]) const ;
-      bool GetTFlag( int nId, int& nFlag) const ;
       bool GetTempInt( int nId, int& nTempInt) const ;
       bool ResetTempInts( void) const ;
-      bool SetTFlag( int nId, int nTFlag) ;
       bool SetTempInt( int nId, int nTempInt) const ;
 
    private :