diff --git a/SurfTriMeshBooleans.cpp b/SurfTriMeshBooleans.cpp
index 2c5b4eb..2e8d065 100644
--- a/SurfTriMeshBooleans.cpp
+++ b/SurfTriMeshBooleans.cpp
@@ -1207,6 +1207,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
          }
       }        
      // Rimuovo il triangolo corrente
+      int nOldTriaCol = m_vTria[it->first].nTFlag ;
       Surf.RemoveTriangle( it->first) ;
      // Trasformo i loop compositi in loop polyline
       POLYLINEVECTOR vplPolyVec ;
@@ -1352,7 +1353,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
                   int nNewId[3] = { Surf.AddVertex( vPt[nNewTriaVertId[0]]),
                                     Surf.AddVertex( vPt[nNewTriaVertId[1]]),
                                     Surf.AddVertex( vPt[nNewTriaVertId[2]]) } ;
-                  int nNewTriaNum = Surf.AddTriangle( nNewId) ;
+                  int nNewTriaNum = Surf.AddTriangle( nNewId, nOldTriaCol) ;
                   if ( IsValidSvt( nNewTriaNum)) {
                      Surf.m_vTria[nNewTriaNum].nETempFlag[0] = 0 ;
                      Surf.m_vTria[nNewTriaNum].nETempFlag[1] = 0 ;
@@ -1445,7 +1446,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
                   int nNewId[3] = { Surf.AddVertex( vPt[nNewTriaVertId[0]]),
                                     Surf.AddVertex( vPt[nNewTriaVertId[1]]),
                                     Surf.AddVertex( vPt[nNewTriaVertId[2]])} ;
-                  int nNewTriaNum = Surf.AddTriangle( nNewId) ;
+                  int nNewTriaNum = Surf.AddTriangle( nNewId, nOldTriaCol) ;
                   if ( IsValidSvt( nNewTriaNum)) {
                      Surf.m_vTria[nNewTriaNum].nETempFlag[0] = 0 ;
                      Surf.m_vTria[nNewTriaNum].nETempFlag[1] = 0 ;
@@ -1468,7 +1469,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
                      int nNewId[3] = { Surf.AddVertex( vPt[nNewTriaVertId[0]]),
                                        Surf.AddVertex( vPt[nNewTriaVertId[1]]),
                                        Surf.AddVertex( vPt[nNewTriaVertId[2]])} ;
-                     int nNewTriaNum = Surf.AddTriangle( nNewId) ;
+                     int nNewTriaNum = Surf.AddTriangle( nNewId, nOldTriaCol) ;
                      if ( IsValidSvt( nNewTriaNum)) {
                         Surf.m_vTria[nNewTriaNum].nETempFlag[0] = 0 ;
                         Surf.m_vTria[nNewTriaNum].nETempFlag[1] = 0 ;