diff --git a/SurfBezier.cpp b/SurfBezier.cpp
index cd57496..44142aa 100644
--- a/SurfBezier.cpp
+++ b/SurfBezier.cpp
@@ -49,7 +49,7 @@
 #define SAVEREBUILTISO 0
 #define SAVERULEDISO 0
 #define SAVERULEDGUIDEDISO 0
-#define SAVEMATCHCURVES 0
+#define SAVEMATCHCURVES 1
 #define SAVEFAILEDTREE 0
 #define SAVELIMITSURF 0
 #if SAVEFAILEDTRIANGULATION  || SAVEREBUILTISO || SAVERULEDISO || SAVERULEDGUIDEDISO  ||  SAVEMATCHCURVES  || SAVEFAILEDTREE  || SAVELIMITSURF
@@ -5722,7 +5722,8 @@ SurfBezier::CreateByTwoCurves( const ICurve* pCurve0, const ICurve* pCurve1, int
                         else
                            dParamMatch = dLastParamMatch0 ;
                         // se lo split non è in prossimità di una joint già esistente allora lo aggiungo
-                        if ( abs( dParamMatch - round( dParamMatch)) > EPS_SMALL  &&  dParamMatch > vdSplit1.back() + EPS_SMALL) {
+                        double dLastSplit = vdSplit1.empty() ? 0 : vdSplit1.back() ;
+                        if ( abs( dParamMatch - round( dParamMatch)) > EPS_SMALL  &&  dParamMatch > dLastSplit + EPS_SMALL) {
                            vdSplit1.push_back( dParamMatch) ;
                            nSplit1 = vdSplit1.size() ;
                         }