diff --git a/evennia/commands/default/player.py b/evennia/commands/default/player.py
index 55919970b..4d03fb813 100644
--- a/evennia/commands/default/player.py
+++ b/evennia/commands/default/player.py
@@ -560,6 +560,7 @@ class CmdOption(COMMAND_DEFAULT_CLASS):
                       "CLIENTNAME": utils.to_str,
                       "ENCODING": validate_encoding,
                       "MCCP": validate_bool,
+                      "MUDPROMPT": validate_bool,
                       "MXP": validate_bool,
                       "NOCOLOR": validate_bool,
                       "NOPKEEPALIVE": validate_bool,