diff --git a/dune/solvers/norms/sumnorm.hh b/dune/solvers/norms/sumnorm.hh
index 7b5555c157f256342ab94b2ff764dac59cf5c98c..b0a8167ec1e53027ece1d2464f70b9c540ee91d6 100644
--- a/dune/solvers/norms/sumnorm.hh
+++ b/dune/solvers/norms/sumnorm.hh
@@ -19,10 +19,10 @@ class SumNorm: public Norm<VectorType>
     //! Compute the norm of the given vector
 		double operator()(const VectorType &v) const
 		{
-			double r1 = norm1(v);
-			double r2 = norm2(v);
-			
-			return std::sqrt(alpha1 * r1 * r1 + alpha2 * r2 *r2);
+			double r1 = norm1.normSquared(v);
+			double r2 = norm2.normSquared(v);
+
+			return std::sqrt(alpha1 * r1 + alpha2 * r2);
 		}
 
     //! Compute the norm of the difference of two vectors