numeric form validation does not work

[eluser]Cgull[/eluser]
Hello,

I have a form with an input field:

Code:

$espresso = array('name'=>'espresso', 'size'=>'1', 'maxlength'=>'3', 'value'=>set_value('espresso'));

In my controller I have this validation rule:

Code:

$this->form_validation->set_rules('espresso', 'Qty', 'trim|numeric');

I put a letter in the espresso field, submit the form and I don't get any error.

If I try this rule:

Code:

$this->form_validation->set_rules('espresso', 'Qty', 'trim|required');

I get a nice beatiful error that the field is required.

Why don't I get the error for the numeric rule?

Thanks