Minecart with Hopper not putting items into containers

What I expected to happen was...:
I thought that droppers would get items from a minecrat with a hopper.

What actually happened was...:
They don't get the items

Steps to Reproduce:
1. Place a dropper.
2. Place any type of rail above the dropper.
3. Place the minecart with the hopper on the rail.
4. Put items inside of the hopper.
5. The items doesn't get sucked in the dropper.