Comment 1 for bug 454591

I've fixed this in the hopefully-soon-to-be-released 11.0. I'll open a task for a workaround for the 10 branch, hopefully to be finished in time for Karmic.

In the meantime, if you want to try the new 11.0 to work around this, you can using the testing PPA: https://launchpad.net/~deja-dup-team/+archive/testing Frankly, this is not recommended if you care about your backup, as it is testing code. Else wait a bit. I hope to release a band-aid 10.3 that will just always pass --allow-source-mismatch (11.0 will actually ask user).