TIL: Converted Rams can be upgraded to Seige Rams

I was my understanding that converted units generally dont receive upgrades. Today on HD I was having a game where I converted a mixture of battering rams and capped rams. Seeing that my opponents were fighting with mostly unique archers and anticipating the 5 rams would not be enough to batter down all the castle I prepared my own seige workshops. When I upgraded to Seige Rams all the converted rams upgraded also. A nice surprise.