It looks like we have overlooked this. We'll fix that for sure.

If you don't want to wait for the fix, you can work around this by modifying `buildSingleOption(...)` method in the `material-select.js` file. Please find the similar line:

this.$materialOptionsList.append($(`<li class="${disabled} ${optgroupClass}">${iconHtml}<span class="filtrable">${checkboxHtml} ${fa} ${$nativeSelectChild.html()}</span></li>`));

And change it to something like this one:

this.$materialOptionsList.append($(`<li class="${disabled} ${optgroupClass} ${$nativeSelectChild.attr('class')}">${iconHtml}<span class="filtrable">${checkboxHtml} ${fa} ${$nativeSelectChild.html()}</span></li>`));

(simply add `$nativeSelectChild.attr('class')` to the `<li>` class list). Then you will have to recompile and re-minify the package to have it in your mdb.min.js file. You can also do exactly the same thing directly in your mdb.js and then re-minify the file to have it in the mdb.min.js file.