diff --git a/ebos/eclbasevanguard.hh b/ebos/eclbasevanguard.hh
index fe2611446..1aac6ae29 100644
--- a/ebos/eclbasevanguard.hh
+++ b/ebos/eclbasevanguard.hh
@@ -296,6 +296,8 @@ public:
     /*!
      * \brief Return compressed index from cartesian index
      *
+     * \return compressed index of cell is in interior, -1 otherwise
+     *
      */
     int compressedIndex(int cartesianCellIdx) const
     {
@@ -306,6 +308,25 @@ public:
             return -1;
     }
 
+    /*!
+     * \brief Return compressed index from cartesian index only in interior
+     *
+     * \return compressed index of cell is in interior, -1 otherwise
+     *
+     */
+    int compressedIndexForInterior(int cartesianCellIdx) const
+    {
+        auto index_pair = cartesianToCompressed_.find(cartesianCellIdx);
+        if (index_pair == cartesianToCompressed_.end() ||
+            !is_interior_[index_pair->second])
+        {
+            return -1;
+        }
+        else
+        {
+            return index_pair->second;
+        }
+    }
     /*!
      * \brief Extract Cartesian index triplet (i,j,k) of an active cell.
      *
@@ -424,9 +445,22 @@ protected:
     void updateCartesianToCompressedMapping_()
     {
         size_t num_cells = asImp_().grid().leafGridView().size(0);
-        for (unsigned i = 0; i < num_cells; ++i) {
-            unsigned cartesianCellIdx = cartesianIndex(i);
-            cartesianToCompressed_[cartesianCellIdx] = i;
+        is_interior_.resize(num_cells);
+        
+        ElementMapper elemMapper(this->gridView(), Dune::mcmgElementLayout());
+        for (const auto& element : elements(this->gridView()))
+        {
+            const auto elemIdx = elemMapper.index(element);
+            unsigned cartesianCellIdx = cartesianIndex(elemIdx);
+            cartesianToCompressed_[cartesianCellIdx] = elemIdx;
+            if (element.partitionType() == Dune::InteriorEntity)
+            {
+                is_interior_[elemIdx] = 1;
+            }
+            else
+            {
+                is_interior_[elemIdx] = 0;
+            }
         }
     }
 
@@ -515,6 +549,10 @@ protected:
     /*! \brief Cell thickness
      */
     std::vector<Scalar> cellThickness_;
+
+    /*! \brief Whether a cells is in the interior.
+     */
+    std::vector<int> is_interior_;
 };
 
 } // namespace Opm
diff --git a/opm/simulators/wells/BlackoilWellModel.hpp b/opm/simulators/wells/BlackoilWellModel.hpp
index a8248c0f8..27e239f4f 100644
--- a/opm/simulators/wells/BlackoilWellModel.hpp
+++ b/opm/simulators/wells/BlackoilWellModel.hpp
@@ -419,8 +419,8 @@ namespace Opm {
 
             void assignWellTracerRates(data::Wells& wsrpt) const;
 
-            int compressedIndex(int cartesian_cell_idx) const override {
-                return ebosSimulator_.vanguard().compressedIndex(cartesian_cell_idx);
+            int compressedIndexForInterior(int cartesian_cell_idx) const override {
+                return ebosSimulator_.vanguard().compressedIndexForInterior(cartesian_cell_idx);
             }
 
         private:
diff --git a/opm/simulators/wells/BlackoilWellModelGeneric.cpp b/opm/simulators/wells/BlackoilWellModelGeneric.cpp
index 5125cefc7..36c28d3f7 100644
--- a/opm/simulators/wells/BlackoilWellModelGeneric.cpp
+++ b/opm/simulators/wells/BlackoilWellModelGeneric.cpp
@@ -349,7 +349,7 @@ initializeWellPerfData()
         parallelWellInfo.beginReset();
 
         for (const auto& completion : well.getConnections()) {
-            const int active_index = compressedIndex(completion.global_index());
+            const int active_index = compressedIndexForInterior(completion.global_index());
             if (completion.state() == Connection::State::OPEN) {
                 if (active_index >= 0) {
                     if (firstOpenCompletion)
diff --git a/opm/simulators/wells/BlackoilWellModelGeneric.hpp b/opm/simulators/wells/BlackoilWellModelGeneric.hpp
index 552df803e..311283637 100644
--- a/opm/simulators/wells/BlackoilWellModelGeneric.hpp
+++ b/opm/simulators/wells/BlackoilWellModelGeneric.hpp
@@ -374,7 +374,8 @@ protected:
     void runWellPIScaling(const int timeStepIdx,
                           DeferredLogger& local_deferredLogger);
 
-    virtual int compressedIndex(int cartesian_cell_idx) const = 0;
+    /// \brief get compressed index for interior cells (-1, otherwise
+    virtual int compressedIndexForInterior(int cartesian_cell_idx) const = 0;
 
 
     Schedule& schedule_;
diff --git a/opm/simulators/wells/BlackoilWellModel_impl.hpp b/opm/simulators/wells/BlackoilWellModel_impl.hpp
index 21402e470..c9ef4e0b1 100644
--- a/opm/simulators/wells/BlackoilWellModel_impl.hpp
+++ b/opm/simulators/wells/BlackoilWellModel_impl.hpp
@@ -125,7 +125,7 @@ namespace Opm {
             for ( size_t c=0; c < connectionSet.size(); c++ )
             {
                 const auto& connection = connectionSet.get(c);
-                int compressed_idx = compressedIndex(connection.global_index());
+                int compressed_idx = compressedIndexForInterior(connection.global_index());
 
                 if ( compressed_idx >= 0 ) { // Ignore connections in inactive/remote cells.
                     wellCells.push_back(compressed_idx);