Problem after upgrade

[Markus T.]

Yesterday I upgraded from version 0.17.5 to 0.91.1 .
Unfortunately, it looks like my spam database file got
corrupted during the process (using bogoupgrade).

When I run the following command:
db4.1_verify spamlist.db

I get this error message:
db_verify: spamlist.db: file size not a multiple of the pagesize
db_verify: DB->open: spamlist.db: Invalid argument

Is it possible to recover my spamlist?
Thanks in advance, Markus