diff --git a/pysipp/command.py b/pysipp/command.py
index 2dcbe8f..5abd5cd 100644
--- a/pysipp/command.py
+++ b/pysipp/command.py
@@ -240,6 +240,7 @@ def todict(self):
     ("-inf {info_files} ", ListField),
     "-screen_file {screen_file} ",
     # bool flags
+    ("-nd {no_default}", BoolField),
     ("-rtp_echo {rtp_echo}", BoolField),
     ("-timeout_error {timeout_error}", BoolField),
     ("-aa {auto_answer}", BoolField),