diff --git a/opm/simulators/wells/BlackoilWellModel_impl.hpp b/opm/simulators/wells/BlackoilWellModel_impl.hpp
index b9bda118b..df95c9c20 100644
--- a/opm/simulators/wells/BlackoilWellModel_impl.hpp
+++ b/opm/simulators/wells/BlackoilWellModel_impl.hpp
@@ -620,7 +620,8 @@ namespace Opm {
         int well_index = 0;
         for (const auto& well : wells_ecl_) {
             int completion_index = 0;
-            int completion_index_above = -1; // -1 marks no above perf available
+            // INVALID_ECL_INDEX marks no above perf available
+            int completion_index_above = ParallelWellInfo::INVALID_ECL_INDEX;
             well_perf_data_[well_index].clear();
             well_perf_data_[well_index].reserve(well.getConnections().size());
             CheckDistributedWellConnections checker(well, *local_parallel_well_info_[well_index]);
diff --git a/opm/simulators/wells/ParallelWellInfo.hpp b/opm/simulators/wells/ParallelWellInfo.hpp
index b7f1ccb5a..f8d0d4b22 100644
--- a/opm/simulators/wells/ParallelWellInfo.hpp
+++ b/opm/simulators/wells/ParallelWellInfo.hpp
@@ -48,8 +48,8 @@ class CommunicateAboveBelow
     using Communication = Dune::CollectiveCommunication<MPIComm>;
 #endif
     using LocalIndex = Dune::ParallelLocalIndex<Attribute>;
+    using IndexSet = Dune::ParallelIndexSet<int,LocalIndex,50>;
 #if HAVE_MPI
-    using IndexSet = Dune::ParallelIndexSet<std::size_t,LocalIndex,50>;
     using RI = Dune::RemoteIndices<IndexSet>;
 #endif
 
@@ -189,6 +189,7 @@ public:
     using Communication = Dune::CollectiveCommunication<MPIComm>;
 #endif
 
+    static constexpr int INVALID_ECL_INDEX = -1;
 
     /// \brief Constructs object using MPI_COMM_SELF
     ParallelWellInfo(const std::string& name = {""},