diff --git a/opm/simulators/flow/Main.hpp b/opm/simulators/flow/Main.hpp
index caaba2130..7a9785c5e 100644
--- a/opm/simulators/flow/Main.hpp
+++ b/opm/simulators/flow/Main.hpp
@@ -664,7 +664,7 @@ private:
     static int getNumThreads()
     {
 
-        int threads = 1;
+        int threads;
 
 #ifdef _OPENMP
         // This function is called before the parallel OpenMP stuff gets initialized.
@@ -681,6 +681,8 @@ private:
             if (input_threads > 0)
                 threads = input_threads;
         }
+#else
+        threads = 1;
 #endif
 
         return threads;
diff --git a/opm/simulators/flow/NonlinearSolverEbos.cpp b/opm/simulators/flow/NonlinearSolverEbos.cpp
index 1ddd5b51f..60833c164 100644
--- a/opm/simulators/flow/NonlinearSolverEbos.cpp
+++ b/opm/simulators/flow/NonlinearSolverEbos.cpp
@@ -90,8 +90,7 @@ void stabilizeNonlinearUpdate(BVector& dx, BVector& dxOld,
         if (omega == 1.) {
             return;
         }
-        auto i = dx.size();
-        for (i = 0; i < dx.size(); ++i) {
+        for (auto i = 0*dx.size(); i < dx.size(); ++i) {
             dx[i] *= omega;
             tempDxOld[i] *= (1.-omega);
             dx[i] += tempDxOld[i];
diff --git a/opm/simulators/wells/MultisegmentWell_impl.hpp b/opm/simulators/wells/MultisegmentWell_impl.hpp
index 01225feab..143c99769 100644
--- a/opm/simulators/wells/MultisegmentWell_impl.hpp
+++ b/opm/simulators/wells/MultisegmentWell_impl.hpp
@@ -887,6 +887,7 @@ namespace Opm
         auto obtain = [this](const Eval& value)
                       {
                           if constexpr (std::is_same_v<Value, Scalar>) {
+                              static_cast<void>(this); // suppress clang warning
                               return getValue(value);
                           } else {
                               return this->extendEval(value);
@@ -989,7 +990,7 @@ namespace Opm
         auto obtain = [this](const Eval& value)
                       {
                           if constexpr (std::is_same_v<Value, Scalar>) {
-                              (void)this; // suppress clang warning
+                              static_cast<void>(this); // suppress clang warning
                               return getValue(value);
                           } else {
                               return this->extendEval(value);
diff --git a/opm/simulators/wells/StandardWell_impl.hpp b/opm/simulators/wells/StandardWell_impl.hpp
index 80172708a..ea3ceb457 100644
--- a/opm/simulators/wells/StandardWell_impl.hpp
+++ b/opm/simulators/wells/StandardWell_impl.hpp
@@ -129,6 +129,7 @@ namespace Opm
         auto obtain = [this](const Eval& value)
                       {
                           if constexpr (std::is_same_v<Value, Scalar>) {
+                              static_cast<void>(this); // suppress clang warning
                               return getValue(value);
                           } else {
                               return this->extendEval(value);
@@ -145,6 +146,7 @@ namespace Opm
         auto zeroElem = [this]()
                         {
                             if constexpr (std::is_same_v<Value, Scalar>) {
+                                static_cast<void>(this); // suppress clang warning
                                 return 0.0;
                             } else {
                                 return Value{this->primary_variables_.numWellEq() + Indices::numEq, 0.0};
@@ -579,7 +581,7 @@ namespace Opm
         auto obtain = [this](const Eval& value)
                       {
                           if constexpr (std::is_same_v<Value, Scalar>) {
-                              (void)this; // suppress clang warning
+                              static_cast<void>(this); // suppress clang warning
                               return getValue(value);
                           } else {
                               return this->extendEval(value);
diff --git a/opm/simulators/wells/WellAssemble.cpp b/opm/simulators/wells/WellAssemble.cpp
index 395bcf2e8..ad1c5fae3 100644
--- a/opm/simulators/wells/WellAssemble.cpp
+++ b/opm/simulators/wells/WellAssemble.cpp
@@ -214,7 +214,7 @@ assembleControlEqInj(const WellState& well_state,
         std::vector<double> convert_coeff(well_.numPhases(), 1.0);
         well_.rateConverter().calcInjCoeff(/*fipreg*/ 0, well_.pvtRegionIdx(), convert_coeff);
 
-        double coeff = 1.0;
+        double coeff;
 
         switch (injectorType) {
         case InjectorType::WATER: {