diff --git a/dune/elasticity/materials/geomexactstvenantkirchhoffmaterial.hh b/dune/elasticity/materials/geomexactstvenantkirchhoffmaterial.hh
index de933faad94093db8cd6b22c08cd67657233f495..d9422865d1f62ff8e8230d8ba489e1ebcfae7a23 100644
--- a/dune/elasticity/materials/geomexactstvenantkirchhoffmaterial.hh
+++ b/dune/elasticity/materials/geomexactstvenantkirchhoffmaterial.hh
@@ -137,9 +137,9 @@ private:
     const Basis& basis_;
 
     //! Elasticity modulus
-    const ctype E_;
+    ctype E_;
     //! Poisson ratio
-    const ctype nu_;
+    ctype nu_;
     
 
     //! Compute nonlinear strain tensor from the deformation gradient.