Could not unpickle M_UNRECOGNIZED: MatrixError: [405] Unrecognized request (.../org.matrix.msc2697.v2/dehydrated_device/claim)

[menturion]

Description

Since upgraded to Synapse v1.78.0 I am getting the below issue:

POST /_matrix/client/unstable/org.matrix.msc2697.v2/dehydrated_device/claim 405
fetch	@	fetch.ts?76d0:62
requestOtherUrl	@	fetch.ts?76d0:264
request	@	fetch.ts?76d0:205
authedRequest	@	fetch.ts?76d0:156
rehydrateDevice	@	client.ts?5faf:1571

could not unpickle M_UNRECOGNIZED: MatrixError: [405] Unrecognized request (/_matrix/client/unstable/org.matrix.msc2697.v2/dehydrated_device/claim)
    at parseErrorResponse (webpack-internal:///120:83:12)
    at MatrixHttpApi.requestOtherUrl (webpack-internal:///116:248:

This might be a regression again, see ...

#14334
matrix-org/matrix-js-sdk#2809

Steps to reproduce

See above.

Homeserver

.

Synapse Version

.

Installation Method

pip (from PyPI)

Database

Both PostgreSQL & SQLITE

Workers

I don't know

Platform

.

Configuration

.

Relevant log output

.

Anything else that would be useful to know?

.

[clokep]

I think this is due to #14605.