diff --git a/LuaLibs/BeamExec.lua b/LuaLibs/BeamExec.lua
index a793209..5d16f02 100644
--- a/LuaLibs/BeamExec.lua
+++ b/LuaLibs/BeamExec.lua
@@ -1333,7 +1333,7 @@ end
 
 -------------------------------------------------------------------------------------------------------------
 function BeamExec.ProcessFeatures()
-   if not BD.IMPROVE_HEAD_TAIL_DRILLINGS then
+   if BD.IMPROVE_HEAD_TAIL_DRILLINGS == nil then
       BD.IMPROVE_HEAD_TAIL_DRILLINGS = true
    end
    -- verifica se possibile rotazione di 90 gradi
diff --git a/LuaLibs/ProcessDrill.lua b/LuaLibs/ProcessDrill.lua
index 471a893..cf836ab 100644
--- a/LuaLibs/ProcessDrill.lua
+++ b/LuaLibs/ProcessDrill.lua
@@ -413,7 +413,11 @@ function ProcessDrill.Make( Proc, nPhase, nRawId, nPartId)
    local dToolAddLength = dLen - dMaxElev
    if dDepth - dToolAddLength > dMaxDepth + 10 * GEO.EPS_SMALL then
       sMyWarn = 'Warning in drill : depth (' .. EgtNumToString( dDepth - dToolAddLength, 1) .. ') bigger than max tool depth (' .. EgtNumToString( dMaxDepth, 1) .. ')'
-      dDepth = dLen
+      if dMaxDepth == 0 then
+         dDepth = 0
+      else
+         dDepth = dLen
+      end
       EgtOutLog( sMyWarn)
    end
    EgtSetMachiningParam( MCH_MP.DEPTH, dDepth)