selectionCssClass setting doesn't work

[KraljN]

I can't apply any css class to select. There is my code:

<Select2 :options="options" :settings="{selectionCssClass: 'form-control'}" v-model="form.region_id" />

I took selectionCssClass from https://select2.org/configuration/options-api as it says in documentation.

Please help.