diff --git a/preptools/command/proposal_setting_command.py b/preptools/command/proposal_setting_command.py
index a27bce3..9e33fc2 100644
--- a/preptools/command/proposal_setting_command.py
+++ b/preptools/command/proposal_setting_command.py
@@ -240,7 +240,7 @@ def create_tx_parser() -> argparse.ArgumentParser:
         "--step-limit", "-s",
         type=str_to_int,
         required=False,
-        default="0x50000000",
+        default=None,
         dest="step_limit",
         help="step limit to set"
     )