Fix group prefix bug.

e32f9bf66f023669a748046fae9c6d030deef9a0 was incomplete.

Change-Id: Ie7c26658c1b44b8a66bd199e4ef3d88f3ea598f2
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>