diff --git a/dune/fufem/basistraceindexset.hh b/dune/fufem/basistraceindexset.hh
index fe22f4ccc29084634a73603eecee5418ba26b938..05ce90d8bd27f39894a30dbde6ab0b62c6cd1a61 100644
--- a/dune/fufem/basistraceindexset.hh
+++ b/dune/fufem/basistraceindexset.hh
@@ -68,8 +68,8 @@ public:
     int index(int fullIndex) {return globalToTraceIndex[fullIndex];}
 
 private:
-    BoundaryPatchType boundary_;
-    GlobalBasis basis_;
+    const BoundaryPatchType& boundary_;
+    const GlobalBasis& basis_;
     std::vector<int> globalToTraceIndex;
     int size_;