Unity 5 - Occlusion culling 2D error

'm trying to set a Occlusion culling on my topdown 2D game. I have made a sprite object with a Occlusion Area on it.Once I try to bake it, it gives me the following error:

No Renderers that are marked static were found in the scene. Please mark all renderers that will never move as static in the inspector. UnityEditor.DockArea:OnGUI()

What exactly does this mean? I have tried making the objects I don't want to render static.

I'm using V5.3.2