Xenial Xerus: Dark Stripe On Horizontal Launcher

As we all Linux/ Ubuntu/ Unity dwellers already know, ever since Xenial Xerus release, you can place the Unity Launcher on the bottom of your screen.
I've tested that right away after the install, and I like it a lot, but, I couldn't help to notice (take a look at the picture on the left) that there is a strange and ugly looking dark "stripe" (or, I don't know, faux shadow, maybe?) if you choose to use the Unity Launcher horizontally.
The same stripe (or whatever) disappears on the Launcher if you place it vertically...