Unable to use API to post new statuses (basic auth problem?)

At some point, I lost the ability to post new statuses through the API:

$ curl -XPOST 'https://ap.barrucadu.co.uk/api/v1/statuses' -H 'content-type: application/json' -d '{"status":"api test"}' -u 'memo:<password>'
{"error":"Insufficient permissions: write:statuses."}

I've confirmed that the credentials are correct (I can log into the frontend with them), and the API docs say basic auth works: https://docs.pleroma.social/backend/API/pleroma_api/. Nothing shows up in the logs.

I'm using the latest release tag of pleroma, though it's been broken for a few releases now (I'm not sure exactly when it first stopped working).