Read Only Field in Multipage Form

I used the instructions in

http://www.gravityhelp.com/forums/topic/make-a-readonly-field#post-7034

to create a read only field.

However this is not working in a multipage form.

When i create a normal page and add css class as disable ginput_container has this

<input name="input_1" id="input_13_1" type="text" value="test" class="medium" tabindex="1" disabled="disabled">

but in a multipage form disabled="disabled" is missing.

How can I add this class in multipage forms?

Why no answer to this question?

Thanks for the reply!