Horses can't go up 1 block while on lead

What I expected to happen was...:
For the horse to follow me while on a lead.

What actually happened was...:
When you lead the horse to any step-up (eg: plains biome, 1 block step-up with no other obstacles (eg: trees) nearby) it can't move up and stops following.

Steps to Reproduce:
1. Tame horse
2. Put lead on horse
3. Find 1 block high step-up
4. Try to walk horse up