  Spatial 't Hooft loops of strength k measure the qualitative change in the
behaviour of electric colour flux in confined and deconfined phase of SU(N)
gauge theory. They show an area law in the deconfined phase, known analytically
to two loop order with a ``k-scaling'' law k(N-k).
  In this paper we compute the O(g^3) correction to the tension.
  It is due to neutral gluon fields that get their mass through interaction
with the wall. The simple k-scaling is lost in cubic order.
  The generic problem of non-convexity shows up in this order.
  The result for large N is explicitely given.
