diff --git a/dune/mmdg/mmdg.hh b/dune/mmdg/mmdg.hh
index a83541dbf9d2d190a9b2c948f63fc04c0adfa8df..be04ec73b588fb28813d483b7863d19c196d0bc3 100644
--- a/dune/mmdg/mmdg.hh
+++ b/dune/mmdg/mmdg.hh
@@ -894,6 +894,7 @@ private:
     //create the output using a linear interpolation for each interface element
     Dune::DynamicVector<Scalar> iPressure(interfaceDOF, 0.0);
     Dune::DynamicVector<Scalar> exactIPressure(interfaceDOF, 0.0);
+    Dune::DynamicVector<Scalar> aperture(interfaceDOF, 0.0);
 
     for (const auto& iElem : elements(iGridView_))
     {
@@ -914,6 +915,9 @@ private:
             Base::problem_.exactInterfaceSolution(iGeo.corner(k));
         }
 
+        aperture[iElemIdxOutput + k] =
+          Base::problem_.aperture(iGeo.corner(k));
+
         //contribution of the basis function
         // phi_iElem,0 (x) = indicator(iElem);
         //at the kth corner of iElem
@@ -934,6 +938,8 @@ private:
       vtkWriter(iGridView_, Dune::VTK::nonconforming);
     vtkWriter.addVertexData( std::shared_ptr<const VTKFunction>(
       new P1Function(iGridView_, iPressure, "interfacePressure")));
+    vtkWriter.addVertexData( std::shared_ptr<const VTKFunction>(
+      new P1Function(iGridView_, aperture, "aperture")));
 
     if (Base::problem_.hasExactSolution())
     {