diff --git a/dune/solvers/iterationsteps/multigridstep.hh b/dune/solvers/iterationsteps/multigridstep.hh
index c18a46132fc89c37910c3bd40a1db1c785b3fb6b..01870d35a847bb7b0e33e3be27b19010bca61924 100644
--- a/dune/solvers/iterationsteps/multigridstep.hh
+++ b/dune/solvers/iterationsteps/multigridstep.hh
@@ -149,7 +149,7 @@
         void setTransferOperators(const DerivedTransferHierarchy& transfer)
         {
             mgTransfer_.resize(transfer.size());
-            for(int j=0; j<transfer.size(); ++j)
+            for(size_t j=0; j<transfer.size(); ++j)
                 mgTransfer_[j] = transfer[j];
         }