Mesh Element with hflex min causes zero width

<zk>
<grid hflex="min">
<rows>
<row>
Row Content
</row>
</rows>
</grid>
<listbox hflex="min">
<listitem>
<listcell>Listitem Content</listcell>
</listitem>
</listbox>
<tree hflex="min">
<treechildren>
<treeitem>
<treerow>
<treecell>Treeitem Content</treecell>
</treerow>
</treeitem>
</treechildren>
</tree>
</zk>