Error: Depth Blend as Vertex offset Input mask

When you use the Depth Blend node as a mask to Vertex offset it didn't compile. I recently discover with a little help of a friend, the "sceneZ" varible is not defined inside the fragment shader when the shader forge attempt to compile.

I am posting some images of the nodes, the error and the shader itself.

http://pastebin.com/McJnY7Wz