Minecarts on top of a block pushed by a piston phase through the block

If a minecart is sitting on top of a block that is on top of a piston that pushes the block upwards the minecart (whether being riden or not) will go through the block. Doesn't matter if said minecart is on a rail. (Which pops off the block... not sure if thats suppose to happen or not).  A minecart sitting on the piston itself however will not go through the piston.