diff --git a/dune/tectonic/mydirectionalconvexfunction.hh b/dune/tectonic/mydirectionalconvexfunction.hh
index 526c9821086fbea9658f502f99a01cd79ddcdeda..c04f6de90f124b99c277d0e9033f6c00a00b5ca9 100644
--- a/dune/tectonic/mydirectionalconvexfunction.hh
+++ b/dune/tectonic/mydirectionalconvexfunction.hh
@@ -10,8 +10,8 @@ template <class NonlinearityType> class MyDirectionalConvexFunction {
   typedef typename NonlinearityType::VectorType VectorType;
   typedef typename NonlinearityType::MatrixType MatrixType;
 
-  MyDirectionalConvexFunction(double A, double b, NonlinearityType const& phi,
-                              const VectorType& u, const VectorType& v)
+  MyDirectionalConvexFunction(double A, double b, NonlinearityType const &phi,
+                              VectorType const &u, VectorType const &v)
       : A(A), b(b), phi_(phi), u_(u), v_(v), temp_u_(u) {
     phi_.directionalDomain(u_, v_, dom_);
   }
@@ -20,7 +20,7 @@ template <class NonlinearityType> class MyDirectionalConvexFunction {
 
   double linearPart() const { return b; }
 
-  void subDiff(double x, Interval<double>& D) const {
+  void subDiff(double x, Interval<double> &D) const {
     temp_u_ = u_;
     temp_u_.axpy(x, v_);
     phi_.directionalSubDiff(temp_u_, v_, D);
@@ -28,7 +28,7 @@ template <class NonlinearityType> class MyDirectionalConvexFunction {
     D[1] += A * x - b;
   }
 
-  void domain(Interval<double>& domain) const {
+  void domain(Interval<double> &domain) const {
     domain[0] = this->dom_[0];
     domain[1] = this->dom_[1];
   }
@@ -37,11 +37,11 @@ template <class NonlinearityType> class MyDirectionalConvexFunction {
   double b;
 
 private:
-  NonlinearityType const& phi_;
-  const VectorType& u_;
-  const VectorType& v_;
+  NonlinearityType const &phi_;
+  VectorType const &u_;
+  VectorType const &v_;
 
-  mutable VectorType temp_u_;
+  VectorType mutable temp_u_;
   Interval<double> dom_;
 };