changing the graphics for existing units

[Zanthis]

I modded my game so that explorers came about with the map making tech. I changed the graphic for the explorer to the scout graphic to make it fit a little better with the era (conquistidors in the ancient era look funny). The problem is that on the world map, the explorer still has the old conquistidor graphic, not the new scout graphic. Oddly, the correct graphic is displayed in the city garison window.

Any ideas what the problem is?