diff --git a/stl_thumb_generator.lua b/stl_thumb_generator.lua
index d75aef8..7a1320c 100644
--- a/stl_thumb_generator.lua
+++ b/stl_thumb_generator.lua
@@ -5,15 +5,17 @@ local cmd = 'stl-thumb'
 
 local function parse_one_level( path )
   for myfile in lfs.dir(path) do
-    local attr = lfs.attributes (myfile)
-    if attr.mode == "directory" then
-      print("Entering sub folder : ", myfile)
-      parse_one_level( myfile)
-    elseif string.match(myfile, "%.stl") or string.match(myfile, "%.STL") then
-      print("Thumbnail for : ", myfile)
-      local fullname = rootpath .. myfile
-      local fullcmd = cmd .. " --format JPG --size 512 " .. fullname .. " " .. fullname .. ".jpg"
-      os.execute( fullcmd )
+    if myfile ~= "." and  myfile ~= ".." then 
+      local attr = lfs.attributes (myfile)
+      if attr.mode == "directory" then
+        print("Entering sub folder : ", myfile)
+        parse_one_level( myfile)
+      elseif string.match(myfile, "%.stl") or string.match(myfile, "%.STL") then
+        print("Thumbnail for : ", myfile)
+        local fullname = rootpath .. myfile
+        local fullcmd = cmd .. " --format JPG --size 512 " .. fullname .. " " .. fullname .. ".jpg"
+        os.execute( fullcmd )
+      end
     end
   end
 end