JSP / JSTL :: Trim Whitespace Directive?

When using trim-directive-whitespaces in a Tomcat 7 application this expression also get trimmed:
 
<div class="${item.view} ${item.className}">
resulting in the HTML
<div class="personchild">
 
instead of
 
<div class="person child">
 
On the other hand, when I first assign the expression to a varibale it's fine:

<c:set var="className" value="${item.view} ${item.className}"/>
<div class="${className}">
 results in the desired HTML
 <div class="person child">
 
Is this the intention of the trim whitespace directive or does this look like a bug?