How to get custom field values from issue via API when customField is a multiselect value

I’m reading Jira issues returned by /search/

When API reads a customField with multi-select value, I can only see [ [Object], {Object],… ] list.

However, with single-select customFields is shown successfully and I can see the “value” field.

How can I see the multi selected values, is there something I need to expand (by query parameter) or is there a workaround?

We just updated from 7.13 enterprise to Jira version 8.5, and the problem still remains.