Online DDL does not behave like expected

ALTER ONLINE TABLE pages  ROW_FORMAT=COMPRESSED    KEY_BLOCK_SIZE=4, ALGORITHM=INPLACE 

+----------------+----------+----------+-------------------------------------------------------------------+

| Table          | Op       | Msg_type | Msg_text                                                          |

+----------------+----------+----------+-------------------------------------------------------------------+

| ccmstats.pages | optimize | note     | Table does not support optimize, doing recreate + analyze instead |

| ccmstats.pages | optimize | error    | Incorrect key file for table 'pages'; try to repair it            |

| ccmstats.pages | optimize | status   | Operation failed                                                  |

+----------------+----------+----------+-------------------------------------------------------------------+

3 rows in set, 1 warning (35.65 sec)

CREATE TABLE `pages` (

  `idUrl` int(10) unsigned NOT NULL,

  `section` tinyint(4) NOT NULL,

  `titre` varchar(100) NOT NULL,

  `description` varchar(255) NOT NULL,

  `idDomaine` tinyint(3) unsigned NOT NULL,

  `solved` tinyint(1) DEFAULT '0',

  PRIMARY KEY (`idDomaine`,`idUrl`),

  KEY `unicity` (`idDomaine`,`section`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1

show table status like 'pages'\G

*************************** 1. row ***************************

           Name: pages

         Engine: InnoDB

        Version: 10

     Row_format: Compressed

           Rows: 7025762

 Avg_row_length: 144

    Data_length: 1015545856

Max_data_length: 0

   Index_length: 39563264

      Data_free: 3145728

 Auto_increment: NULL

    Create_time: 2014-11-14 14:40:55

    Update_time: NULL

     Check_time: NULL

      Collation: latin1_swedish_ci

       Checksum: NULL

 Create_options: row_format=COMPRESSED key_block_size=4

        Comment: