Need help to setup searchable Attribute

Hey guys, i am using refinement list.

        container: '#filter-widgets-languages',
        attributesForFaceting: [
        attribute: 'language_names',
        sortBy: ['name:asc'],
        limit: 5,
        showMore: false,
        searchable: true,
        searchablePlaceholder: 'Search by languages',
        searchableIsAlwaysActive: false,
        searchableEscapeFacetValues: false,
        searchableLoadingIndicator: 'loading',
        transformData: {
          item: data => {
            data.count = 0;
            return data;

when I am running it, it throws: Cannot search in language_names attribute, you need to add searchable(language_names) to attributesForFaceting.

Any lead/hint would be helpful.
thank you in advance.