
Originally Posted by
dennis580
I think that is because if you have Gunpowder (Rifle) and Bronze Working (Archers) but Not Democracy(Pikes), you can build both Archers AND Rifles because Pikes are needed to make Archers obsolete.
(in the demo I rushed Steam Power before it was built... and my Galley didn't change because I didn't have Navigation for the Galleons)
I would say this qualifies as a bug, but at least it is a predictable bug.
That doesn't sound like a bug at all, but it looks like the way the game makers intended it to be. A unit has to be totally obsolete before it can be upgraded.