diff --git a/LuaLibs/PreSimulationLib.lua b/LuaLibs/PreSimulationLib.lua
index 08b3588..66384e9 100644
--- a/LuaLibs/PreSimulationLib.lua
+++ b/LuaLibs/PreSimulationLib.lua
@@ -385,7 +385,7 @@ local function CheckCollisionWithAxis( sAxis, MachiningParameters, OptionalParam
    local vtSCC = BeamLib.GetDirectionFromSCC( nSCC)
    local vtC = vtHead ^ Tool.SetupInfo.vtRotationAxisC
    vtC:normalize()
-   if vtC:isZero() then
+   if vtC:isSmall() then
       vtC = vtSCC
    elseif vtC * vtSCC < GEO.EPS_SMALL then
       vtC = -vtC