Woohoo! Fixed. I created an empty file, then used copyTransactionsFrom to copy all transactions across. This patched the backpointers. fsrecover.py should probably get some smarts to do something like this as well, but I've spent far too long on this problem already... :-/ from ZODB import FileStorage infilename='/app/zope/dev_csr_server/recover/Data.fs' outfilename='/app/zope/dev_csr_server/recover/Out.fs' outfs = FileStorage.FileStorage(outfilename) infs = FileStorage.FileStorage(infilename) outfs.copyTransactionsFrom(infs) I have some small patches to fsdump that outputs expected prev records alongside the actual ones, is this useful enough to check in? Anthony