XhtmlException error when using a variable as a macro parameter in page blueprint

<ac:structured-macro ac:name="detailssummary" ac:schema-version="2">
    <ac:parameter ac:name="firstcolumn">Release</ac:parameter>
    <ac:parameter ac:name="headings">Category,Type, Description</ac:parameter>
    <ac:parameter ac:name="pageSize">100</ac:parameter>
    <ac:parameter ac:name="sortBy">title</ac:parameter>
    <ac:parameter ac:name="label">mylabel</ac:parameter>
    <ac:parameter ac:name="cql"><at:var at:name="myvariablename"/></ac:parameter>
</ac:structured-macro>

Error: RuntimeException occurred while performing an XHTML storage transformation (com.atlassian.confluence.content.render.xhtml.XhtmlException: Unhandled element type '{http://atlassian.com/template}var')