A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'ID'

I can't figure out why I get this error when I try to add a Venue object and call SaveChanges(). The only difference in the model with Venue objects is they are 1 to 1..0 relation with City.

City city = ProcessCityCache(ev, country, db); // After this call, 'city' is already persisted.
venue = new Venue {
    TicketMasterURL = ev.VenueSeoLink,
    Name = Capitalize(ev.VenueName),
    City = city
};
db.Venues.AddObject(venue);
db.SaveChanges(); // Exception thrown here.

Any insight would be greatly appreciated!

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