diff --git a/dune/solvers/norms/diagnorm.hh b/dune/solvers/norms/diagnorm.hh
index 54a86fccd73bff3b5c1257c525d9209872eebb73..cc6ea40b70e6ed79d5101b33dd64b8e374a353f3 100644
--- a/dune/solvers/norms/diagnorm.hh
+++ b/dune/solvers/norms/diagnorm.hh
@@ -74,7 +74,7 @@ class DiagNorm<Dune::BlockVector<Dune::FieldVector <double,1> >, Dune::BlockVect
         {
             double r = 0.0;
 
-            for(int row = 0; row < v.size(); ++row)
+            for(size_t row = 0; row < v.size(); ++row)
                 r += d[row] * v[row] * v[row];
 
             return sqrt(fabs(alpha * r));
@@ -85,7 +85,7 @@ class DiagNorm<Dune::BlockVector<Dune::FieldVector <double,1> >, Dune::BlockVect
         {
             double r = 0.0;
 
-            for(int row = 0; row < v1.size(); ++row)
+            for (size_t row = 0; row < v1.size(); ++row)
                 r += (double)d[row] * (v1[row]-v2[row]) * (v1[row] - v2[row]);
 
             return sqrt(fabs(alpha * r));
diff --git a/dune/solvers/norms/fullnorm.hh b/dune/solvers/norms/fullnorm.hh
index 564368259d051c8dcc86e161f93bab81dda36cf2..b503325c4dcf75bb6340c695d94b7190c4aea542 100644
--- a/dune/solvers/norms/fullnorm.hh
+++ b/dune/solvers/norms/fullnorm.hh
@@ -30,7 +30,7 @@ class FullNorm: public Norm<VectorType>
             r = 0.0;
 
             lowRankFactor_.umv(v,r);
-//            for(int row = 0; row < v.size(); ++row)
+//            for (size_t row = 0; row < v.size(); ++row)
 //                r += m[row] * v[row];
 
             return sqrt(fabs(alpha*(r*r)));
@@ -76,7 +76,7 @@ class FullNorm<Dune::BlockVector<Dune::FieldVector<double,1> >, Dune::BlockVecto
         {
             double r = 0.0;
 
-            for(int row = 0; row < v.size(); ++row)
+            for (size_t row = 0; row < v.size(); ++row)
                 r += m[row] * v[row];
 
             return sqrt(fabs(alpha*r*r));
@@ -87,7 +87,7 @@ class FullNorm<Dune::BlockVector<Dune::FieldVector<double,1> >, Dune::BlockVecto
         {
             double r = 0.0;
 
-            for(int row = 0; row < v1.size(); ++row)
+            for (size_t row = 0; row < v1.size(); ++row)
                 r += (double)m[row] * (v1[row] - v2[row]);
 
             return sqrt(fabs(alpha*r*r));