modifyStyle() and addLessVariables not working

Hi, I’m making a child theme and following the code from Default theme, I’ve done this:

    $this->setParent('defaultthemeplugin');

    $additionalLessVariables = array();

    if (Config::getVar('general', 'enable_cdn')) {
        if ($this->getOption('typography') !== 'notoSans') {
            $this->removeStyle('fontNotoSans');
        }

        if ($this->getOption('typography') === 'merriweather') {
            $this->addStyle(
                'fontMerriweather',
                '//fonts.googleapis.com/css?family=Merriweather:400,400i,700,700i',
                array('baseUrl' => '')
            );
            $additionalLessVariables[] = '@font: "Merriweather", Georgia, serif;';
        }
    }

    // Pass additional LESS variables based on options
    if (!empty($additionalLessVariables)) {
        $this->modifyStyle('stylesheet', array('addLessVariables' => join($additionalLessVariables)));
    }

The problem is when calling addLessVariables, it looks like another variables from Default theme (like colors) lose their value. Any idea what could be happening? The same happens if I put any variable instead. I just want to replace the @font var.

Nevermind, it looks like I have to set the variables again according to the Manuscript Theme