Why is Blender "overcompensating" edges on normal maps, and how can I stop it? Wikipedia has this example of normal maps:

I put the normal map into Blender myself and got this:

Why is there a dark ridge around the edge of each shape? Based on the specularities around the edge of the donut, it looks to me like Blender is &quot;overcompensating&quot; every bump by surrounding it with a ditch (and vice versa). How do I stop this behaviour to get the correct edges?
(This is a minimal example of the more complex problem I'm facing.)
EDIT: These are the exact steps I took to reproduce:

Open Blender 2.79b.
UV map the default cube to this image.
Alter the default material's &quot;Tex&quot; texture so that instead of Color 1.0, it influences Normal 1.0. (No nodes are involved.)


That's all. I have tried changing the Color Space, but like all other times I've tried, changing it has no effect.
You must check Normal Map under the Image Sampling options of the texture.

Also, make sure to set the color-space to non-color data.