temper tantrums

I didn't think 6 month olds had temper tantrums yet but my little guy has been throwing a fit lately when I change his clothes. I had just been letting it go thinking he's not old enough to understand he's being bad but I got tired of it and yelled "stop! That's enough!" And he stopped and smiled at me! What a stinker! I know sometimes he cries and something is really bothering him but this whole screaming every time I change him has to stop. Anyone else's little ones already starting to protest when they don't get their way?