diff --git a/dumux/decoupled/2p2c/2p2cproblem.hh b/dumux/decoupled/2p2c/2p2cproblem.hh
index d2f1e430f190940e490f31f826e94678e5490c77..f88409ac4fc29b5de30fd917b6d042e57a8f0b8e 100644
--- a/dumux/decoupled/2p2c/2p2cproblem.hh
+++ b/dumux/decoupled/2p2c/2p2cproblem.hh
@@ -202,7 +202,7 @@ protected:
         else if (equation == -1)
         {
             // set everything to zero
-            for (int i = 0; i < values.size(); i++)
+            for (unsigned int i = 0; i < values.size(); i++)
                 values[i] = 0.;
         }
         else
diff --git a/dumux/implicit/3p3c/3p3cmodel.hh b/dumux/implicit/3p3c/3p3cmodel.hh
index 849fd3cbec67203955ca0c010ed599ab45ac25ac..52db59e9f02ac945891076c5ae249edd818cce85 100644
--- a/dumux/implicit/3p3c/3p3cmodel.hh
+++ b/dumux/implicit/3p3c/3p3cmodel.hh
@@ -508,7 +508,7 @@ protected:
      */
     void resetPhasePresence_()
     {
-        for (int i = 0; i < this->numDofs(); ++i)
+        for (unsigned int i = 0; i < this->numDofs(); ++i)
         {
             staticDat_[i].phasePresence
                 = staticDat_[i].oldPhasePresence;
@@ -521,7 +521,7 @@ protected:
      */
     void updateOldPhasePresence_()
     {
-        for (int i = 0; i < this->numDofs(); ++i)
+        for (unsigned int i = 0; i < this->numDofs(); ++i)
         {
             staticDat_[i].oldPhasePresence
                 = staticDat_[i].phasePresence;
diff --git a/dumux/implicit/cellcentered/ccassembler.hh b/dumux/implicit/cellcentered/ccassembler.hh
index 081a24ea722a0634bde386210de48a5e3c364219..eea8f575ebe7c8002ec8204053c01c4c89ca3369 100644
--- a/dumux/implicit/cellcentered/ccassembler.hh
+++ b/dumux/implicit/cellcentered/ccassembler.hh
@@ -123,7 +123,7 @@ private:
         }
         
         // set the discrepancy of the red elements to zero
-        for (int i = 0; i < this->delta_.size(); i++)
+        for (unsigned int i = 0; i < this->delta_.size(); i++)
             if (this->elementColor_[i] == ParentType::Red)
                 this->delta_[i] = 0;
     }
diff --git a/dumux/implicit/common/implicitassembler.hh b/dumux/implicit/common/implicitassembler.hh
index cd0550d2782a31abe14de717292fc448da4bb117..4b4081cf80d1eee604d7907492b754d4fc0e4aba 100644
--- a/dumux/implicit/common/implicitassembler.hh
+++ b/dumux/implicit/common/implicitassembler.hh
@@ -418,7 +418,7 @@ protected:
 
             // reset the parts needed for Jacobian recycling
             if (enableJacobianRecycling_()) {
-                for (int i = 0; i < matrix_->N(); i++) {
+                for (unsigned int i = 0; i < matrix_->N(); i++) {
                     storageJacobian_[i] = 0;
                     storageTerm_[i] = 0;
                 }
@@ -458,7 +458,7 @@ protected:
         // here and be done with it...
         Scalar curDt = problem_().timeManager().timeStepSize();
         if (reuseMatrix_) {
-            for (int i = 0; i < matrix_->N(); i++) {
+            for (unsigned int i = 0; i < matrix_->N(); i++) {
                 // rescale the mass term of the jacobian matrix
                 MatrixBlock &J_i_i = (*matrix_)[i][i];