Inserting fixture data with a primary key of 0

This doesn't seem to work on mysql, at least. We depend on this
functionality as we're porting an old app over to rails; does anyone
know where I can find out how to disable the magic going on here?

I don't think this isn't a rails thing (at least I can see anything in
the fixtures code for that). on the other hand, the mysql
documentation says:

Normally, you generate the next sequence number for the column by inserting either NULL or 0 into it.
NO_AUTO_VALUE_ON_ZERO suppresses this behavior for 0 so that only NULL generates the next sequence number.