--- src/inadyn_cmd.c.orig	Fri May  6 13:40:40 2011
+++ src/inadyn_cmd.c	Fri May  6 13:41:14 2011
@@ -650,7 +650,7 @@ static RC_TYPE set_change_persona_handler(CMD_DATA *p_
 			}
 		}
 
-		if (sscanf(arg, "%[a-z]", username) != 1)
+		if (sscanf(arg, "%[_a-z]", username) != 1)
 		{
 			return RC_DYNDNS_INVALID_OPTION;
 		}