Disabling merge of classes?

Hello,

I'd like to make tidy stop merging classes in consecutive divs (e.g.):

<div class="first">
	<div class="second">	
		text
	</div>
</div>

should not be merged to

<div class="first second">
	text
</div>


Is there an option or another way of making tidy drop doing this?
I couldn't find anything...


best regards
Steffen Glückselig