Player riding saddled pig trample farmland by walking

The bug

When walking on farmland blocks while riding on a saddled pig the farmland revert to dirt blocks. I have only tested it while holding a carrot on a stick.
Isolated farmland, i.e. farmland blocks surrounded by non-farmland blocks, seem to be immune from this. It happens with hydrated farmland as well as dehydrated farmland. Saddled pigs with no mounted player on them do not trample farmland by walking on it.