diff --git a/script/local.py b/script/local.py
index d97c636..fcb9e9d 100644
--- a/script/local.py
+++ b/script/local.py
@@ -45,7 +45,8 @@ class RobotModbus(DeviceBase):
         args = [0,0,0,0,0,0]
         index = 0        
         for arg in argv:
-            args[index++] = arg
+            args[index] = arg
+            index = index + 1
         robot_args.write(args)
         robot_req.write(1)
         try: