Unity prevents usage of "Super R" as "Switch to next source" keyboard shortcut

[Kabanov Dmitry]

I set "Super R" key as my shortcut to change keyboard layouts. See attached screenshot.

What happens:

Whenever I press "Super R" key, Unity intercepts it and use it to open the Dash. I haven't found any options in Unity Tweak Tool or Compiz Settings Manager to prevent Unity from doing this. Aforementioned utilities do not distinguish between Left Super and Right Super keys.

Expected behavior:
Unity should use only left Super key for opening the Dash.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: unity 7.2.2+14.04.20140714-0ubuntu1.1
ProcVersionSignature: Ubuntu 3.13.0-35.62-generic 3.13.11.6
Uname: Linux 3.13.0-35-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.3
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CurrentDesktop: Unity
Date: Thu Sep 4 15:09:57 2014
InstallationDate: Installed on 2014-08-28 (6 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)