diff --git a/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.cpp b/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.cpp
index 1271fd7eaf..c4b4c67962 100644
--- a/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.cpp
+++ b/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.cpp
@@ -118,7 +118,7 @@ class RigOpmFlowDiagStaticData : public cvf::Object
 {
 public:
     RigOpmFlowDiagStaticData( const ecl_grid_type*            mainGrid,
-                              const std::string&              init,
+                              const std::wstring&             init,
                               RiaEclipseUnitTools::UnitSystem caseUnitSystem )
     {
         Opm::ECLInitFileData initData( init );
@@ -516,8 +516,8 @@ bool RigFlowDiagSolverInterface::ensureStaticDataObjectInstanceCreated()
     if ( m_opmFlowDiagStaticData.isNull() )
     {
         // Get set of files
-        QString     gridFileName = m_eclipseCase->gridFileName();
-        std::string initFileName = getInitFileName();
+        QString      gridFileName = m_eclipseCase->gridFileName();
+        std::wstring initFileName = getInitFileName();
         if ( initFileName.empty() ) return false;
 
         const RigEclipseCaseData* eclipseCaseData = m_eclipseCase->eclipseCaseData();
@@ -992,18 +992,18 @@ bool RigFlowDiagSolverInterface::calculatePvtDynamicPropertiesViscosity(
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
-std::string RigFlowDiagSolverInterface::getInitFileName() const
+std::wstring RigFlowDiagSolverInterface::getInitFileName() const
 {
     QString gridFileName = m_eclipseCase->gridFileName();
 
     QStringList m_filesWithSameBaseName;
 
     if ( !RifEclipseOutputFileTools::findSiblingFilesWithSameBaseName( gridFileName, &m_filesWithSameBaseName ) )
-        return std::string();
+        return std::wstring();
 
     QString initFileName = RifEclipseOutputFileTools::firstFileNameOfType( m_filesWithSameBaseName, ECL_INIT_FILE );
 
-    return initFileName.toStdString();
+    return initFileName.toStdWString();
 }
 
 //--------------------------------------------------------------------------------------------------
diff --git a/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.h b/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.h
index 95bbaa4825..7df20264f7 100644
--- a/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.h
+++ b/ApplicationCode/ReservoirDataModel/RigFlowDiagSolverInterface.h
@@ -157,11 +157,11 @@ public:
         size_t activeCellIndex, double pressure, double rs, double rv, double* mu_o, double* mu_g );
 
 private:
-    std::string getInitFileName() const;
-    bool        ensureStaticDataObjectInstanceCreated();
-    void        assignPhaseCorrecedPORV( RigFlowDiagResultAddress::PhaseSelection phaseSelection, size_t timeStepIdx );
-    void        reportRelPermCurveError( const QString& message );
-    void        reportPvtCurveError( const QString& message );
+    std::wstring getInitFileName() const;
+    bool         ensureStaticDataObjectInstanceCreated();
+    void         assignPhaseCorrecedPORV( RigFlowDiagResultAddress::PhaseSelection phaseSelection, size_t timeStepIdx );
+    void         reportRelPermCurveError( const QString& message );
+    void         reportPvtCurveError( const QString& message );
 
     RimEclipseResultCase*              m_eclipseCase;
     cvf::ref<RigOpmFlowDiagStaticData> m_opmFlowDiagStaticData;