PHP Warning: chmod(): Operation not permitted in class-wp-filesystem-direct.php on line 173

I running an instance of Wordpress on my web server but I'm getting this error in the logs

PHP Warning:  chmod(): Operation not permitted in 
/home/webserver/html/wp-admin/includes/class-wp-filesystem-direct.php on line 173, 
referer: http:// mysite.com/

I check the class-wp-filesystem-direct.php file on 173

here is the line:

if ( ! $recursive || ! $this-is_dir( $file ) ) {
                        return chmod( $file, $mode );
}

This are the permissions of this file:

-rwxrwxr-x 1 root apache 17K Oct 20 20:24 /home/webserver/html/wp-admin/includes/class-wp-filesystem-direct.php

Any of you knows what is wrong with my instance of Wordpress?

I'll really appreciated your help.