Bug with virtual field

CREATE TABLE stocks (

  codeart VARCHAR(20) DEFAULT '',

  num_lot VARCHAR(20) DEFAULT '',

  depot VARCHAR(20) DEFAULT '',

  qte_init DOUBLE DEFAULT 0,

  qte DOUBLE DEFAULT 0,

  cmdclient DOUBLE DEFAULT 0,

  qte_verr DOUBLE DEFAULT 0,

  cmdfour DOUBLE DEFAULT 0,

  rebut DOUBLE DEFAULT 0,

  recycl DOUBLE DEFAULT 0,

  qte_fac_init DOUBLE DEFAULT 0,

  qte_fac DOUBLE DEFAULT 0,

  ug DOUBLE DEFAULT 0,

  pmp_init DOUBLE DEFAULT 0,

  pmp DOUBLE DEFAULT 0,

  pmp_rebut DOUBLE DEFAULT 0,

  pmp_recycl DOUBLE DEFAULT 0,

  valstock DOUBLE AS (`qte` * `pmp`) VIRTUAL,

  valstock_rebut DOUBLE AS (`rebut` * `pmp_rebut`) VIRTUAL,

  valstock_recycl DOUBLE AS (`stocks`.`recycl` * `pmp_recycl`) VIRTUAL,

  qte_dispo DOUBLE AS (`qte` - `cmdclient`) VIRTUAL,

  INDEX IDX_stocks_codeart (codeart),

  INDEX IDX_stocks_depot (depot),

  INDEX IDX_stocks_num_lot (num_lot),

  UNIQUE INDEX UK_stocks (codeart, num_lot, depot)

)

ENGINE = INNODB

AVG_ROW_LENGTH = 655

CHARACTER SET utf8

COLLATE utf8_unicode_ci

ROW_FORMAT = DYNAMIC;