binlog_do_db not working? (MySQL 5.1.68)

[Italo Tasso]

I used the options:

binlog-format=ROW
binlog-do-db=cobrafix

They seem to be set ok:

mysql> show master status\G;
*************************** 1. row ***************************
File: mysql-bin.000002
Position: 13174
Binlog_Do_DB: cobrafix
Binlog_Ignore_DB:
1 row in set (0.00 sec)

mysql> show variables\G;
*************************** 10. row ***************************
Variable_name: binlog_format
Value: ROW

But on the binary log, I have:

[root@cobrafix mysql]# mysqlbinlog mysql-bin.000002

/*!*/;
# at 1962
#130323 9:00:01 server id 1 end_log_pos 2077 Query thread_id=159 exec_time=0 error_code=0
use `cobrafix`/*!*/;
SET TIMESTAMP=1364040001/*!*/;
DROP TABLE IF EXISTS cobrafix_crystal.temp_c_328
/*!*/;
# at 2077
#130323 9:00:01 server id 1 end_log_pos 6098 Query thread_id=159 exec_time=0 error_code=0
SET TIMESTAMP=1364040001/*!*/;
CREATE TABLE cobrafix_crystal.temp_c_328 (

Why is MySQL logging database cobrafix_crystal, since it is not on the binlog_do_db?