ducklake catalog backup fails on 'Missing Extension Error'

[nyc-de]

I am following the ducklake docs to create a backup.

Following the postgres -> duckdb instructions verbatim yields an error.

Am I missing an extension or...?

ATTACH 'postgres:connection_string' AS db (READ_ONLY);
ATTACH 'duckdb:backup.duckdb' AS backup;
COPY FROM DATABASE db TO backup;

Missing Extension Error:
Cannot bind index 'ducklake_snapshot_changes', unknown index type ''. You need to load the extension that provides this index type before table 'ducklake_snapshot_changes' can be modified.