Issue when baking normals from BI node materials.

I’m sure this isn’t an actual bug so much as me just forgetting how it’s done. I know that I’ve done this before, but I have either completely forgotten the process, it has changed, or an additional step that I’m unware of has been added. Basically, after constructing procedural materials in the Blender Internal or Blend Game rendering environment, the result is an entirely blue image as if no normals information is being passed to the bake process, even though they’re visible on the model in Material and Rendered view modes. I can still bake normals using non-node based materials, but when using the nodes, anything I plug into the “Normal” socket, though visible on screen, doesn’t produce output when baked. If that’s confusing, hopefully the following image clears things up.

I’m not entirely sure what I’ve forgotten, or what I’m doing wrong, but I’m looking for any solution I can find. Thanks in advance.