DjangoCMS 3.7

Hi, I have a question.

I am using DjangoCMS 3.7, Django 2.1.7 and Bootstrap4 1.3.1 and it works fine.

But if I change the version of Django to 2.2.7 it doesn't work. 
I see the following message in the browser console : TypeError: $ element.select2 is not a function (django_select2.js:48:14)

Can you help me?

Thank you.