diff --git a/CMakeLists_files.cmake b/CMakeLists_files.cmake
index 28648cbc..1a6c4bb0 100644
--- a/CMakeLists_files.cmake
+++ b/CMakeLists_files.cmake
@@ -124,6 +124,7 @@ list (APPEND MAIN_SOURCE_FILES
 	opm/core/transport/reorder/TransportSolverTwophaseReorder.cpp
 	opm/core/transport/reorder/reordersequence.cpp
 	opm/core/transport/reorder/tarjan.c
+	opm/core/utility/compressedToCartesian.cpp
 	opm/core/utility/Event.cpp
 	opm/core/utility/MonotCubicInterpolator.cpp
 	opm/core/utility/StopWatch.cpp
diff --git a/opm/core/utility/compressedToCartesian.cpp b/opm/core/utility/compressedToCartesian.cpp
new file mode 100644
index 00000000..641ee817
--- /dev/null
+++ b/opm/core/utility/compressedToCartesian.cpp
@@ -0,0 +1,48 @@
+/*
+  Copyright 2015 SINTEF ICT, Applied Mathematics.
+
+  This file is part of the Open Porous Media project (OPM).
+
+  OPM is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  OPM is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#include <opm/core/utility/compressedToCartesian.hpp>
+#include <numeric>
+
+namespace Opm
+{
+
+    // Construct explicit mapping from active/compressed to logical cartesian
+    // indices, either as given in global_cell or as { 0, 1, 2, ....} if null.
+    // \param[in] num_cells    The number of active cells.
+    // \param[in] global_cell  Either null, or an array of size num_cells.
+    // \return                 A vector containing the same data as global_cell,
+    //                         or the sequence { 0, 1, ... , num_cells - 1 } if
+    //                         global_cell was null.
+    std::vector<int> compressedToCartesian(const int num_cells,
+                                           const int* global_cell)
+    {
+        std::vector<int> retval;
+        if (global_cell) {
+            retval.assign(global_cell, global_cell + num_cells);
+        } else {
+            retval.resize(num_cells);
+            std::iota(retval.begin(), retval.end(), 0);
+        }
+        return retval;
+    }
+
+
+} // namespace Opm
diff --git a/opm/core/utility/compressedToCartesian.hpp b/opm/core/utility/compressedToCartesian.hpp
index 9b84e2fc..83a5ebc1 100644
--- a/opm/core/utility/compressedToCartesian.hpp
+++ b/opm/core/utility/compressedToCartesian.hpp
@@ -33,20 +33,8 @@ namespace Opm
     // \return                 A vector containing the same data as global_cell,
     //                         or the sequence { 0, 1, ... , num_cells - 1 } if
     //                         global_cell was null.
-    inline
     std::vector<int> compressedToCartesian(const int num_cells,
-                                           const int* global_cell)
-    {
-        std::vector<int> retval;
-        if (global_cell) {
-            retval.assign(global_cell, global_cell + num_cells);
-        } else {
-            retval.resize(num_cells);
-            std::iota(retval.begin(), retval.end(), 0);
-        }
-        return retval;
-    }
-
+                                           const int* global_cell);
 
 } // namespace Opm