diff --git a/CurveAux.cpp b/CurveAux.cpp
index cd163d0..f25c5b9 100644
--- a/CurveAux.cpp
+++ b/CurveAux.cpp
@@ -1137,7 +1137,7 @@ FindSpan( double dU, int nDeg, const DBLVECTOR& vKnots, int& nSpan)
    // trovo a quale span appartiene il parametro dU
    int nKnots = int( vKnots.size()) ;
    if ( abs( dU - vKnots[nKnots-1]) < EPS_SMALL) {
-      nSpan = nKnots - 1 ;
+      nSpan = nKnots - 1 - nDeg ;
       return true ;
    }
    int nLow = nDeg - 1 ;