Update hasone relation behaves strangely (cakephp)

I've got an existing Showcase that hasOne Gallery.
The Gallery already exists with the foreignKey showcase_id set to the proper value.
The Gallery has a text field that I try to update via the Showcase-controller.
The result I get is an extra Gallery entry, along the original one, instead of an update of the original entry.

What am I doing wrong?

My Showcase-view looks as follows:

echo $form->create('Showcase', array('action'=>'update'));

echo $form->input('Showcase.id', array('type'=>'hidden', 'value'=>$showcase['Showcase']['id']));

echo $form->input('Gallery.fulltext', array('type'=>'textarea', 'between'=>'
', 'value'=>$showcase['Gallery']['fulltext']));

echo $form->submit('Submit text');

echo $form->end();

My Showcase-controller function:

$uses = array('Showcase','Gallery')

function update(){

if(!empty($this->data)){

$this->Showcase->saveAll($this->data, array('validate'=>'first'));

}

}

The Showcase model $hasOne = 'Gallery' and the Gallery model $belongsTo = 'Showcase'.

Is $this->Showcase->saveAll() the proper function to use here? Or do I maybe need to update the Gallery entry within the Gallery controller? That will probably work but is seems so un-elegant.