Gitlab api get merge request approved_by_ids

Hello,

I am trying to use the gitlab API to get the merge requests approved by a given user.

I crafted a request that looked like this:

GET /projects/:project/merge_requests?state=merged&approved_by_ids[]=:user-id&private_token=:token

However, in the resulting list I receive all merge requests not only approved by the user but all merge request where the user was an eligible approver even if he did not approved.

I also tried with the groups

GET /groups/:group/merge_requests?state=merged&approved_by_ids[]=:user-id&private_token=:token

I got similar results.

We are using self-managed gitlab (12.5.4-ee).

What did I miss?

Thanks for the help,
Benoit

It appears that approved_by_ids was introduced in 12.8. We are using 12.5. I was reading wrong version of the API documentation.