diff --git a/usb_application/simtrace.py b/usb_application/simtrace.py
index 9730cf5a..9ea938e9 100755
--- a/usb_application/simtrace.py
+++ b/usb_application/simtrace.py
@@ -52,7 +52,7 @@ def find_dev():
 # main code
 def main():
     parser = argparse.ArgumentParser()
-    parser.add_argument("-C", "--conf", type=int, choices=[1, 2, 3], help="Set USB config")
+    parser.add_argument("-C", "--conf", type=int, choices=[1, 2, 3, 4], help="Set USB config")
     parser.add_argument("-b", "--read_bin", help="read ICCID, IMSI, etc.", action='store_true')
     parser.add_argument("-c", "--cmd", help="cmds to send to sim card (Not supported yet)", 
         choices=["cmd1", "cmd2", "cmd_poweron", "cmd_poweroff", "cmd_get_slot_stat", "cmd_get_param"])