hecarim E auto used after connecting on snowball

In Howling Abyss as Hecarim, if you have your E activated and connect on a snowball (second cast, flying to target), your E will automatically proc on the target where you land, even when you spam click another target. I'm pretty sure this is not meant to be since the E procs on next basic attack, and a basic attack is not supposed to proc after connecting on a snowball.

Steps to reproduce this:

1. Land a snowball in Howling Abyss
2. Activate your E
3. Activate snowball again (fly to your target)

Then you will automatically charge onto the target you flew to.