Cannot read property 'util' of undefined

[augustosamame]

I am getting the following error when implementing a select2 with SimpleForm and this gem:

Cannot read property 'util' of undefined

This is the offending line:

var stripDiacritics = window.Select2.util.stripDiacritics;

JS error in console:

initializers.select2_simple_form.self-3b52a09c2e096725f4dfa3a398c74cc1a370d8b810a433a627531d241f5eef4a.js?body=1:42 Uncaught TypeError: Cannot read property 'util' of undefined
at prepareSelect2Options (initializers.select2_simple_form.self-3b52a09c2e096725f4dfa3a398c74cc1a370d8b810a433a627531d241f5eef4a.js?body=1:42)
at HTMLSelectElement. (initializers.select2_simple_form.self-3b52a09c2e096725f4dfa3a398c74cc1a370d8b810a433a627531d241f5eef4a.js?body=1:137)
at Function.each (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:371)
at jQuery.fn.init.each (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:138)
at HTMLDocument.initializeSelect2SimpleForm (initializers.select2_simple_form.self-3b52a09c2e096725f4dfa3a398c74cc1a370d8b810a433a627531d241f5eef4a.js?body=1:134)
at HTMLDocument.dispatch (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:5227)
at HTMLDocument.elemData.handle (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:4879)
at Object.trigger (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:5131)
at jQuery.fn.init.triggerHandler (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:5867)
at Function.ready (jquery.self-bd7ddd393353a8d2480a622e80342adf488fb6006d667e8b42e4c0073393abee.js?body=1:3587)

[ifsc01]

some issue