Teleporting with a commandblock, while riding a pig doesn't work.

I expected teleporting with the pig, to the coordinates I entered into the command block.

What actually happends:
I only see the location where I wanted to teleport to for a brief second, and then I'm back at the location where I started.

1. Put down a command block, and enter the command /tp @ [x] [y] [z]
2. Link the command block to a pressure plate.
3. Go over the pressure plate while riding a pig.
4. Then the bugs happens, and you will not get teleported to the coordinates given.