VertexnormalWS with displacement in landscape only works in Z. Now what?

Is there a trick to make vertexnormalWS work with world position offset displacement in landscapes? I can only displace in z and the node just ignores X and Y. I want to create some small hangovers this way. In tesselation it seems to work but i would like to have it work with world position also. (Non directx users) regards! T