Okay, let me rephrase myself, it was not a sound play. And to be calling/raising with the ace rag is normally unprofitable, but I was pretty damn sure he had the underpair, and in this situation my hand was good.
Now I look back on it the raise may have indeed signified a strong ace, protecting from the 2 diamonds on the board, so maybe I was just lucky that my "read" was correct.