JSmin + doesn't support let and drupalSettings

JSMinPlus had a possible error minifying, missing operand on line 1 disappears when I remove drupalSettings from js file, so basically changing this line:
(function ($, Drupal, drupalSettings) {
to:
(function ($, Drupal) {
gets rid of this error, but doesn't fix my problem as I still need drupalSettings in this file.

Another thing I noticed is that "JSMinPlus had a possible error minifying, Error: Parse error: Missing ; before statement in file '[inline]' on line x" error gets fixed for me, when I change "let" to "var", so it seems like "let" is not supported