diff --git a/LuaLibs/CalcToolPath.lua b/LuaLibs/CalcToolPath.lua
index 98fc96f..881c8c5 100644
--- a/LuaLibs/CalcToolPath.lua
+++ b/LuaLibs/CalcToolPath.lua
@@ -1683,6 +1683,10 @@ end
 ---------------------------------------------------------------------------------
 local function FindCorrectRibLead( dPar, nRib, nCrvOffs, bLeadInvert, dLeadLen, bInVsOut, nGrpTmp, bSpecialCase)
    
+   if dLeadLen < GEO.EPS_SMALL then
+      return
+   end
+   
    local nLeadId
    local bInvert = bLeadInvert    -- valore di default è quello dei parametri
    local bOnlyOneSide = false