diff --git a/dune/gfe/harmonicenergystiffness.hh b/dune/gfe/harmonicenergystiffness.hh
index 9081a26526213f9ba1bb85559e46d8aacf171d6a..8a8ea8f7bf9b71895fa9182ad21bb92476bbaa89 100644
--- a/dune/gfe/harmonicenergystiffness.hh
+++ b/dune/gfe/harmonicenergystiffness.hh
@@ -7,6 +7,10 @@
 #include "localgeodesicfestiffness.hh"
 #include "localgeodesicfefunction.hh"
 
+#ifdef HARMONIC_ENERGY_FD_GRADIENT
+#warning Finite-difference approximation of the energy gradient
+#endif
+
 template<class GridView, class TargetSpace>
 class HarmonicEnergyLocalStiffness 
     : public LocalGeodesicFEStiffness<GridView,TargetSpace>