Google is complaining about missing field entry-title

In webmaster tools I am getting the message that the class entry-title is missing in my page titles.

I have digged into the code and found out that the titles are generated by a function in
kleo\lib\theme-functions.php

around line 374 it says

$title_data = ”;
if( $show_title )
{
$title_data = ‘<{heading} class=”page-title”>{title}</{heading}>’;
}

How can I make it to look like this (adding class entry-title)

$title_data = ”;
if( $show_title )
{
$title_data = ‘<{heading} class=”page-title entry-title”>{title}</{heading}>’;
}

in my child theme?

This is not a pluggable function. How to proceed here? I have now changed the code in my parent theme. But this is not a permanent solution.
Thanks for any help on this.