diff --git a/dune/gfe/riemanniantrsolver.hh b/dune/gfe/riemanniantrsolver.hh
index e5f682f7265384b0675e3f648870d91ccf8be880..98e3869f6b02dec1b79cdb2bfb3630694f2f4841 100644
--- a/dune/gfe/riemanniantrsolver.hh
+++ b/dune/gfe/riemanniantrsolver.hh
@@ -39,7 +39,9 @@ class RiemannianTrustRegionSolver
     typedef Dune::BlockVector<Dune::FieldVector<field_type, blocksize> >           CorrectionType;
     typedef std::vector<TargetSpace>                                               SolutionType;
 
-#ifdef SECOND_ORDER
+#ifdef THIRD_ORDER
+#error RiemannianTrustRegionSolver cannot currently be used for third-order spaces
+#elif defined SECOND_ORDER
     typedef Dune::GlobalP2Mapper<typename GridType::LeafGridView> GUIndex;
 #else
     typedef GlobalUniqueIndex<typename GridType::LeafGridView, gridDim> GUIndex;