diff --git a/dune/solvers/norms/h1seminorm.hh b/dune/solvers/norms/h1seminorm.hh
index e8ceaa45e264dd625b820bfd761f34cac233dbb7..b2bb5cc8d2724a750e65e17bf08f786be59f91ba 100644
--- a/dune/solvers/norms/h1seminorm.hh
+++ b/dune/solvers/norms/h1seminorm.hh
@@ -21,7 +21,7 @@ public:
 	{
 		double sum = 0;
 		
-		for (int i=0; i<matrix_->N(); i++) 
+		for (size_t i=0; i<matrix_->N(); i++) 
 		{
 			typename Dune::BCRSMatrix<Dune::FieldMatrix<double,1,1> >::row_type::const_iterator cIt    = (*matrix_)[i].begin();
 			typename Dune::BCRSMatrix<Dune::FieldMatrix<double,1,1> >::row_type::const_iterator cEndIt = (*matrix_)[i].end();