Changes in default.php seem to be ignored

After updating WordPress to 4.0.1 und the plugin to it’s newest version, I’m missing the changes I defined in default.php.
The file is in the plugin’s folder in the child theme folder, but somehow it does not take effect on the output.
Needed to replace the

• -tags in the source with <div>.
  These are now gone for the moment.
  Any idea where to look for a solution?
  Thanks.
  T. Lüers

https://wordpress.org/plugins/list-category-posts/