diff --git a/dune/tectonic/myblockproblem.hh b/dune/tectonic/myblockproblem.hh
index c413a0bf459f1cbc85ec0244a9c4176f4c2562cf..078ec7b3b55951970ecf625678973d6cde3044fc 100644
--- a/dune/tectonic/myblockproblem.hh
+++ b/dune/tectonic/myblockproblem.hh
@@ -27,7 +27,8 @@ template <class MyConvexProblemTypeTEMPLATE> class MyBlockProblem {
   /** \brief Solves one local system using a modified gradient method */
   class IterateObject;
 
-  MyBlockProblem(Dune::ParameterTree &parset, MyConvexProblemType &problem)
+  MyBlockProblem(Dune::ParameterTree const &parset,
+                 MyConvexProblemType &problem)
       : parset(parset), problem(problem) {
     bisection = Bisection(
         0.0, // acceptError: Stop if the search interval has
@@ -49,7 +50,7 @@ template <class MyConvexProblemTypeTEMPLATE> class MyBlockProblem {
   // commonly used minimization stuff
   Bisection bisection;
 
-  Dune::ParameterTree &parset;
+  Dune::ParameterTree const &parset;
 };
 
 /** \brief Solves one local system using a scalar Gauss-Seidel method */
@@ -62,7 +63,7 @@ class MyBlockProblem<MyConvexProblemTypeTEMPLATE>::IterateObject {
    * \param bisection The class used to do a scalar bisection
    * \param problem The problem including quadratic part and nonlinear part
    */
-  IterateObject(Dune::ParameterTree &parset, Bisection const &bisection,
+  IterateObject(Dune::ParameterTree const &parset, Bisection const &bisection,
                 MyConvexProblemType &problem)
       : parset(parset), problem(problem), bisection(bisection) {}
 
@@ -129,7 +130,7 @@ class MyBlockProblem<MyConvexProblemTypeTEMPLATE>::IterateObject {
   }
 
 private:
-  Dune::ParameterTree &parset;
+  Dune::ParameterTree const &parset;
 
   // problem data
   MyConvexProblemType &problem;