Hi, I was able to reproduce following the steps detailed in the description. This is also happening for latest community mysql (5.5.43), I can provide outputs if needed (in this case I also have outputs for a slave that didn't have slow logs enabled, for which replication didn't break). FROM MASTER: +---------------+-------+ | Variable_name | Value | +---------------+-------+ | log_output | FILE | +---------------+-------+ +------------------------------------+-----------------------------------------------------------------------------+ | Variable_name | Value | +------------------------------------+-----------------------------------------------------------------------------+ | slow_query_log | ON | | slow_query_log_file | /home/agustin.gallego/sandboxes/msb_tmp-ps5_5_42/data/bm-support01-slow.log | +------------------------------------+-----------------------------------------------------------------------------+ FROM SLAVE: +---------------+-------+ | Variable_name | Value | +---------------+-------+ | log_output | FILE | +---------------+-------+ +------------------------------------+-----------------------------------------------------------------------------------+ | Variable_name | Value | +------------------------------------+-----------------------------------------------------------------------------------+ | slow_query_log | ON | | slow_query_log_file | /home/agustin.gallego/sandboxes/msb_tmp-ps-slave5_5_42/data/bm-support01-slow.log | +------------------------------------+-----------------------------------------------------------------------------------+ FOR BOTH: mysql> show variables like '%version%'; +-------------------------+------------------------------------------------------+ | Variable_name | Value | +-------------------------+------------------------------------------------------+ | innodb_version | 5.5.42-37.1 | | protocol_version | 10 | | slave_type_conversions | | | version | 5.5.42-37.1-log | | version_comment | Percona Server (GPL), Release 37.1, Revision 39acee0 | | version_compile_machine | x86_64 | | version_compile_os | Linux | +-------------------------+------------------------------------------------------+ Issued the mysql_upgrade in the master node: $ ./mysql_upgrade --host=127.0.0.1 --port=5542 --force --user=msandbox --password=msandbox Looking for 'mysql' as: ./mysql Looking for 'mysqlcheck' as: ./mysqlcheck Running 'mysqlcheck' with connection arguments: '--host=127.0.0.1' '--port=5542' Running 'mysqlcheck' with connection arguments: '--host=127.0.0.1' '--port=5542' mysql.columns_priv OK mysql.db OK mysql.event OK mysql.func OK mysql.general_log OK mysql.help_category OK mysql.help_keyword OK mysql.help_relation OK mysql.help_topic OK mysql.host OK mysql.ndb_binlog_index OK mysql.plugin OK mysql.proc OK mysql.procs_priv OK mysql.proxies_priv OK mysql.servers OK mysql.slow_log OK mysql.tables_priv OK mysql.time_zone OK mysql.time_zone_leap_second OK mysql.time_zone_name OK mysql.time_zone_transition OK mysql.time_zone_transition_type OK mysql.user OK test.t1 OK Running 'mysql_fix_privilege_tables'... OK SHOW SLAVE STATUS\G output to prove replication stops with that error: mysql [localhost] {msandbox} (test) > show slave status\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: localhost Master_User: msandbox Master_Port: 5542 Connect_Retry: 60 Master_Log_File: mysql-bin.000002 Read_Master_Log_Pos: 48193 Relay_Log_File: mysql_sandbox5543-relay-bin.000002 Relay_Log_Pos: 32304 Relay_Master_Log_File: mysql-bin.000002 Slave_IO_Running: Yes Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 1580 Last_Error: Error 'You cannot 'ALTER' a log table if logging is enabled' on query. Default database: 'mysql'. Query: 'ALTER TABLE slow_log MODIFY start_time TIMESTAMP NOT NULL, MODIFY user_host MEDIUMTEXT NOT NULL, MODIFY query_time TIME NOT NULL, MODIFY lock_time TIME NOT NULL, MODIFY rows_sent INTEGER NOT NULL, MODIFY rows_examined INTEGER NOT NULL, MODIFY db VARCHAR(512) NOT NULL, MODIFY last_insert_id INTEGER NOT NULL, MODIFY insert_id INTEGER NOT NULL, MODIFY server_id INTEGER UNSIGNED NOT NULL, MODIFY sql_text MEDIUMTEXT NOT NULL' Skip_Counter: 0 Exec_Master_Log_Pos: 32158 Relay_Log_Space: 48507 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULL Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 1580 Last_SQL_Error: Error 'You cannot 'ALTER' a log table if logging is enabled' on query. Default database: 'mysql'. Query: 'ALTER TABLE slow_log MODIFY start_time TIMESTAMP NOT NULL, MODIFY user_host MEDIUMTEXT NOT NULL, MODIFY query_time TIME NOT NULL, MODIFY lock_time TIME NOT NULL, MODIFY rows_sent INTEGER NOT NULL, MODIFY rows_examined INTEGER NOT NULL, MODIFY db VARCHAR(512) NOT NULL, MODIFY last_insert_id INTEGER NOT NULL, MODIFY insert_id INTEGER NOT NULL, MODIFY server_id INTEGER UNSIGNED NOT NULL, MODIFY sql_text MEDIUMTEXT NOT NULL' Replicate_Ignore_Server_Ids: Master_Server_Id: 1 1 row in set (0.00 sec)