.tpl Inheritance doesn’t seem to work.

I can’t seem to get the .tpl template inheritance to work as in http://www.smarty.net/inheritance .
I am trying to create a standard layout template with custom content populated on specific pages.

The example is straight forward but I seem to be getting errors Smarty Error: [in /mnt/project/templates/themeName/pages/homePage.tpl line 1]: syntax error: unrecognized tag 'extends'
The contents of my homePage.tpl file:
{extends file="layout.tpl"}
{block name=title}My Page Title{/block}
{block name=body}My HTML Page Body goes here{/block}

Is it possible to extend a .tpl in WHMCS?