SaveAll fails when adding multiple checks to single model field

I have a model with an email field, the validator definition of the field is this:
'email' => array(
'email' => array(
'rule' => 'email',
'message' => 'Please specify a valid email address',
),
),

and it works. As soon as I add an isUnique validator to the same field:
'email' => array(
'email' => array(
'rule' => 'email',
'message' => 'Please specify a valid email address',
),
'unique' => array(
'rule' => 'isUnique',
'message' => 'This email address has already been registered',
),
),

saveAll fails with the following error:
Warning (2): Illegal string offset 'user_id' [CORE/Cake/Model/Model.php, line 2094]
I'm getting mad about this! I'm using Cake 2.0.6.

thanks
--
Lorenzo Milesi - lorenzo.milesi@yetopen.it

YetOpen S.r.l. - http://www.yetopen.it/

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