On downhill track, minecart passes through extended sticky piston blocks

*What I expected to happen was...: The block should have stopped/blocked the minecart just as blocks do when placed manually rather then by sticky piston.

What actually happened was...:
Minecart passes through block (on extended piston). If passenger in minecart, they clip through block, taking damage.

Steps to Reproduce:
1. Build downward slope.
2. Put minetrack on it (all types of track are affected).
3. Place block on some point directly above diagonal track (so that it blocks a minecart when it runs into it).
4. Place piston on right or left side of this block, but one space back (so that it picks up block when extended and pulls block out of path of rail when sticky piston is not powered).
5. Power piston with torch or circuit so piston is extended and block is blocking the rail.
6. Ride minecart through block (all blocks are affected)