Cube sinking slightly into Plane - Unity 4.3

Hi all, I’ve created a new project in Unity 4.3.

All I did was the following:

  1. Add a default plane game object
  2. Add a default cube game object (1x1x1)
  3. Change the cube transform y position coordinate to 0.5 so the cube is sitting on top of the plane
  4. Add a default rigidbody component to cube

When I click play, the cube sinks into the plane a small fraction (going off the cube transform the y-coordinate changes from 0.5 to 0.48). It doesn’t fall through. The only visual difference is a very slight vertical drop (however, the properties as per the screenshot below seem to suggest otherwise).

I have verified that plane transform properties are as follows (default):
position x=0, y=0, z=0
rotation x=0, y=0, z=0
scale x=1, y=1, z=1

Is this a bug in Unity 4.3? Thanks a lot for your help.

Cube properties before pressing play:

Cube properties after pressing play:

Go to Edit > Project Settings > Physics. Change the ‘Min Penetration for Penalty’ setting to 0.0.