OK thanks. I have come up with a workaround:
# aptitude purge libssl1.0.0
Choose: The following actions will resolve these dependencies:
Downgrade the following packages:
1) libssl1.0.0 [1.0.2-1 (experimental, now) -> 1.0.1k-1 (unstable)]
2) openssl [1.0.2-1 (experimental, now) -> 1.0.1k-1 (unstable)]
# aptitude forbid-version libssl1.0.0 openssl-- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected]

