Not able to override plugin’s default css rules
If you want to do it this way, it has to look like the following: add_filter(‘style_loader_src’, ‘wpse127340_replace_stylesheet’, 10, 2); function wpse127340_replace_stylesheet($src, $handle){ if (‘your-plugin-script-handle’ == $handle) return get_template_directory_uri().’/css/themes-copy-of-plugin.css’; return $src; } Replace your-plugin-script-handle and themes-copy-of-plugin.css with what you want it to be.