diff --git a/amdis/gridfunctions/CoordsGridFunction.hpp b/amdis/gridfunctions/CoordsGridFunction.hpp
index ed657d093168f7612eb2d95354e7acc0236e7ed2..2512f186d7c15f38529659e45917271b496110fb 100644
--- a/amdis/gridfunctions/CoordsGridFunction.hpp
+++ b/amdis/gridfunctions/CoordsGridFunction.hpp
@@ -44,7 +44,7 @@ namespace AMDiS
       struct Derivative
       {
         template <class T, int N>
-        Dune::DiagonalMatrix<T, N> const& operator()(Dune::FieldVector<T, N> const& /*x*/) const
+        Dune::DiagonalMatrix<T, N> operator()(Dune::FieldVector<T, N> const& /*x*/) const
         {
           return Dune::DiagonalMatrix<T,N>{T(1)};
         }