Attribute with_labels_details does not work for single epic search

I want to use the Gitlab API to receive information about an epic.
I have the id and iid of the epic and want to get the detailed label information.
The documentation (Epics API | GitLab) let me tried the following request:


I get the information about the specific epic, that’s good, but unfortunately I do not get detailed label information. The JSON looks like:

"labels": [

How can I get the detailed label information for an epic by id or iid?

We are using self-managed GitLab Enterprise Edition [15.5.4-ee].