How to make canonical links on joomshopping pagination pages?

Question

Joomla

Catalog category pages have an address like /parfumeriya.html?start=100 The
canonical link should be /parfumeriya.html
I found the code that adds the canon. link (insert in category_default.php):

<?php $document = JFactory::getDocument(); $docstart = JRequest::getInt('start',0); $docroute = rtrim(JURI::root(), '/').JRoute::_('index.php?option=com_jshopping&controller=category&task=view&category_id=' . $this->category->category_id . ''); if($docstart > 0) { $document->addHeadLink($docroute, 'canonical', 'rel', ''); }?>

But the link is /catalog/parfum/ , which doesn't work for me.
Are there any other solutions?