How to reproduce ?

• First I set up the latest master of the anki-sync-server
• Then I go to apps.ankiweb.net and download the latest stable release (2.1.22).
• After that I follow the instructions in the Readme to setup my sync server in Anki.
• Now I hit synchronize

Expected behavior

Everything synchronizes just fine

Actual behavior

I get a dialog with the message

Your client is using unsupported sync protocol (10, supported version: 9)

Additional information

The message is issued in sync_app.py#L90