Uncaught error when I upgrade from 3.5 to 4.0.3

[h-parekh]

I just started working on a new project to fix some accessibility issues. We're using select2-rails 3.5 and I want to upgrade to 4.0.3, but it gives me this error and the dropdown doesn't display at all.

Uncaught Error: No select2/compat/initSelection
    at callDep (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:210)
    at req (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:371)
    at select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:185
    at Defaults.apply (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:4382)
    at new Options (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:4682)
    at new Select2 (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:4809)
    at HTMLInputElement.<anonymous> (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:5342)
    at Function.each (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:371)
    at jQuery.fn.init.each (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:138)
    at jQuery.fn.init.$.fn.select2 (select2.self-e556f1e10512b96e0eb9f7c6cab8f56b461ea4b7f2ec6d63a329e3fba5aa5b41.js?body=1:5339)

[OpenCoderX]

Seems like this is resolved and.or not an issue, closing for now.