"Incorrect table definition" error on upgrade

I just tried to upgrade to version 6.x-1.10 of epublish, and got the following error upon running update.php:

user warning: Incorrect table definition; there can be only one auto column and it must be defined as a key query: ALTER TABLE epublish_edition DROP PRIMARY KEY in /[path to my web directory]/includes/database.mysql-common.inc on line 394.

The Available Updates page is now showing epublish as being version 6.x-1.10, and everything seems to be working OK, but I'm a little worried about that error...