This used to work in Confluence 5.4.3. Since upgrading to 5.5.6, I can no longer update a user's @mention thumbnail picture.

As there is no REST equivalent for this method, we'd really appreciate a fix or workaround.

Reproduction:

1. Use the sample Python script to upload a 48x48 picture.
2. User's @mention picture will show the generic unset avatar
3. User's full profile picture in their homepage shows the correct avatar

Workaround:

Trigger a reindex via Confluence Admin > Content Indexing