In 2.8.3 history for contacts with spaces in usernames was saved as e.g. "john email@example.com". In 2.9.0 it creates a folder "john" and inside of it "firstname.lastname@example.org". It can't gracefully handle the space and creates a folder instead of \ and adds 20 to the history name file, which comes from space escaping "\20" string. Because of that history files are not used when upgrading from older version of Spark.