diff --git a/dune/mmdg/problems/mmdgproblem6.hh b/dune/mmdg/problems/mmdgproblem6.hh
index c1f9d63886ff9f48c38b1aef8f66ee401f9906e2..afec3955f679e93ab010acb5ca76248f7d44faa2 100644
--- a/dune/mmdg/problems/mmdgproblem6.hh
+++ b/dune/mmdg/problems/mmdgproblem6.hh
@@ -10,6 +10,8 @@ class MMDGProblem6 : public CoupledDGProblem<Coordinate, Scalar>
 {
 public:
   static constexpr int dim = Coordinate::dimension;
+  using Base = CoupledDGProblem<Coordinate, Scalar>;
+  using Matrix = typename Base::Matrix;
 
   //constructor
   MMDGProblem6 (const Scalar d0) : d0_(d0), xi_(1.0) {}
@@ -61,7 +63,7 @@ public:
     const Scalar hyperbolicFactor =
       (coshsqrt2 * coshsqrt2 - (2 * xi_ - 1) * sinhsqrt2 * sinhsqrt2);
 
-    return -16.0 * d0_ * d0_ * std::exp(-8.0 * pos[1]) * hyperbolicFactor * (
+    return -16.0 * aperture(pos) * d0_ * d0_ * std::exp(-8.0 * pos[1]) * hyperbolicFactor * (
       cos4y + 3.0 * std::sin(4.0 * pos[1]) ) - sqrt2 * std::sinh(sqrt2) * cos4y;
   }
 
@@ -86,6 +88,19 @@ public:
     return sqrt(2.0) / std::tanh(sqrt(2.0));
   }
 
+  //tangential permeability tensor of the interface at position pos
+  Matrix Kparallel (const Coordinate& pos) const
+  {
+    Matrix permeability(0.0);
+
+    for (int i = 0; i < dim; i++)
+    {
+      permeability[i][i] = 1.0 * aperture(pos);//d_;
+    }
+
+    return permeability;
+  }
+
   //returns the recommended quadrature order to compute an integral
   //over x * boundary(x)
   int quadratureOrderBoundary () const