W3C validation error with orderform with price field

Hi,

I am creating an order form for a site, which includes a price field.
If I validate the form via validator.w3.org I get errors:
The for attribute of the label element must refer to a form control.
…l class='gfield_label' for='input_2_9'>Folder lerarenopleiding HL hbo-master</…

The HTML is:

<li id='field_2_9' class='gfield           gfield_price gfield_price_2_9 gfield_product_2_9' >
<label class='gfield_label' for='input_2_9'>Folder lerarenopleiding HL hbo-master</label>
<div class='ginput_container'><input type='hidden' name='input_9.1' value='Folder lerarenopleiding HL hbo-master' class='gform_hidden' /><span class='ginput_product_price_label'>Prijs:</span> <span class='ginput_product_price' id='input_2_9'>€ 0,00</span>
<input type='hidden' name='input_9.2' id='ginput_base_price_2_9' class='gform_hidden' value='€ 0,00'/>
<span class='ginput_quantity_label'>Aantal:</span> <input type='text' name='input_9.3' value='' id='ginput_quantity_2_9' class='ginput_quantity' size='10' tabindex='1'/></div>
</li>

Kind regards,
Rian Rietveld