Zombie in a boat and mine cart don't burn in the sun...

I have no idea if this is just the area where they are but I had two villagers one in a boat and an other one in a mine cart that got turned into zombies which is OK because it has to be my fault for leaving them outside in a pen with a moat around it.

Usually the zombie vilager will die after being turned in the sun but these two who where in a boat and minecart didn't die.