diff --git a/dune/solvers/transferoperators/genericmultigridtransfer.hh b/dune/solvers/transferoperators/genericmultigridtransfer.hh
index 60f0bc5a1b7451776c4601bffeb832bdf3dc00c0..c1f0780f52d57c9bce97f6c1e2711dc66a925069 100644
--- a/dune/solvers/transferoperators/genericmultigridtransfer.hh
+++ b/dune/solvers/transferoperators/genericmultigridtransfer.hh
@@ -53,7 +53,7 @@ public:
     }
 
     template<class MatrixType>
-    static bool diagonalIsOne(const MatrixType& A, int j)
+    static bool diagonalIsOne(const MatrixType& A, unsigned int j)
     {
         if (j>=A.N())
             return A[0][0]>1-1e-5;
diff --git a/dune/solvers/transferoperators/truncatedcompressedmgtransfer.cc b/dune/solvers/transferoperators/truncatedcompressedmgtransfer.cc
index e1d1c3dcb930ffcc02aeef76aa390924192dc0a0..3883973dac3c5dab9eb0fd53efd77ce83bd9d077 100644
--- a/dune/solvers/transferoperators/truncatedcompressedmgtransfer.cc
+++ b/dune/solvers/transferoperators/truncatedcompressedmgtransfer.cc
@@ -22,7 +22,7 @@ void TruncatedCompressedMGTransfer<DiscFuncType, BitVectorType, OperatorType>::p
     
     Iterator tIt      = t.begin();
 
-    for(int rowIdx=0; rowIdx<this->matrix_->N(); rowIdx++) {
+    for(size_t rowIdx=0; rowIdx<this->matrix_->N(); rowIdx++) {
 
         const RowType& row = (*this->matrix_)[rowIdx];
 
@@ -139,7 +139,7 @@ galerkinRestrict(const OperatorType& fineMat, OperatorType& coarseMat,
   }
 
   // Loop over all rows of the stiffness matrix
-  for (int v=0; v<fineMat.N(); v++) {
+  for (size_t v=0; v<fineMat.N(); v++) {
       
       const RowType& row = fineMat[v];