Downgrade issues

NixOS und Nix support downgrade of packages and their configuration. That works without issues with most programs, but some complain when their state (config. not managed by NixOS, some kind of database, ...) was created with a newer version. This page exist to collect those cases.

Warning: If you know you might have to downgrade again later, create a backup before an upgrade!

Note: If you know a program that does not work well after a downgrade, please add it here with it's behavior and error message. Try to maintain alphabetic order.

Atom

Forgets open files, unsaved text is lost.

Electrum

Can't open wallet created with newer version.

This version of Electrum is too old to open this wallet.
(highest supported storage version: 40, version of this file: 41)

Signal

Start fails with error message. Offers to "delete data and close". Then start and link again to mobile device.

Database startup error:

Error: Error: SQL: User version is 54 but the expected maximum version is 43. Did you try to start an old version of Signal?
...

Syncthing

Refuses to start when downgraded.

[root@nixos:~]# journalctl -u syncthing.service
...
WARNING: Failed to initialize config: config file version (36) is newer than supported version (35). If this is expected, use -allow-newer-config to override

syncthing will however store a copy of its configuration when upgrading next to config.xml, so you might be able to shut down syncthing, take a backup up the new file and then copy the old file into place.