Duplicity: switch to "secondary backup chain"

I ran duplicity when my backup drive wasn't connected, and it deleted lots of cached sigtar and manifest files: Synchronizing remote metadata to local cache... Deleting local /Users/justin/.cache/duplicity/a7190bc7f0d9f083cbc7e03931a8c95f/duplicity-full-signatures.20160608T054248Z.sigtar.gz (not authoritative at backend). Deleting local /Users/justin/.cache/duplicity/a7190bc7f0d9f083cbc7e03931a8c95f/duplicity-full.20160608T054248Z.manifest (not authoritative at backend). Deleting local /Users/justin/.cache/duplicity/a7190bc7f0d9f083cbc7e03931a8c95f/duplicity-inc.20160608T054248Z.to.20160610T041839Z.manifest (not authoritative at backend). Deleting local /Users/justin/.cache/duplicity/a7190bc7f0d9f083cbc7e03931a8c95f/duplicity-inc.20160610T041839Z.to.20160616T043456Z.manifest (not authoritative at backend). Now, when I run duplicity, it tries to do a full backup instead of finding my existing incremental backups. Running duplicity collection-status file:///Volumes/DuplicityBackup/ shows that my backup chain has become a "secondary backup chain", and there is an empty "primary backup chain": $ duplicity collection-status file:///Volumes/DuplicityBackup/ Synchronizing remote metadata to local cache... Last full backup date: Thu Jul 28 22:17:39 2016 Collection Status ----------------- Connecting with backend: LocalBackend Archive dir: /Users/justin/.cache/duplicity/a7190bc7f0d9f083cbc7e03931a8c95f Found 1 secondary backup chain. Secondary chain 1 of 1: ------------------------- Chain start time: Tue Jun 7 22:42:48 2016 Chain end time: Wed Jul 27 07:19:47 2016 Number of contained backup sets: 23 Total number of contained volumes: 2329 Type of backup set: Time: Num volumes: Full Tue Jun 7 22:42:48 2016 2219 Incremental Thu Jun 9 21:18:39 2016 20 Incremental Wed Jun 15 21:34:56 2016 6 Incremental Fri Jun 17 07:29:49 2016 1 ... ------------------------- Found primary backup chain with matching signature chain: ------------------------- Chain start time: Thu Jul 28 22:17:39 2016 Chain end time: Thu Jul 28 22:17:39 2016 Number of contained backup sets: 1 Total number of contained volumes: 0 Type of backup set: Time: Num volumes: ------------------------- No orphaned or incomplete backup sets found. **How can I fix this?** (ie, delete the empty "primary backup chain" and use the "secondary backup chain")