Form Helper postLink won't work with image

echo $this->Form->postLink($this->Html->image("img/iconDelete_25.png"), ['action' => 'delete', $user->id], ['confirm' => __('Are you sure you want to delete this user?', $user->id)]);

The postLink Helper won’t work with the image Helper. Is this a bug or not allowed?
The image path is correct but it will only show the alternative text.

Argh... this is the solution.
<?php echo $this->Form->postLink(
					    $this->Html->image(
					        "hkw/iconDelete_25.png", 
					        ["alt" => __('Delete')]
					    ), 
					    ['controller' => 'clients', 'action' => 'delete', $user->id],
					    ['escape' => false, 'confirm' => __('Are you sure you want to delete this user?', $user->id)]
					)?>