On the 'Code Event Listeners' page it says 'Showing 2 of 2 items' but none are shown.
Checked the table 'xf_code_event_listener' and saw that the column 'addon_id' still had my old ID. Updated it manually and they appeared again.
Same for the table 'xf_route_prefix' and probably some more I didn't bother to check.
I'm guessing that's not how it supposed to work anyway.