htaccess filesMatch or Files gives 500 when trying to set headers

 For example, if you have something like this on your .htaccess,

# One year for image files
<filesMatch ".(jpg|jpeg|png|gif|ico|woff|woff2|svg)$">
Header set Cache-Control "max-age=31536000, public"
</filesMatch>

or

# Allow JSON files to be accessed from anywhere
<Files "*.json">
  Header set Access-Control-Allow-Origin "*"
</Files>

You will need to have headers mod enabled. To do so,

 sudo a2enmod headers