diff --git a/src/opm/output/eclipse/EclipseIO.cpp b/src/opm/output/eclipse/EclipseIO.cpp
index fc250b677..e0bb1b226 100644
--- a/src/opm/output/eclipse/EclipseIO.cpp
+++ b/src/opm/output/eclipse/EclipseIO.cpp
@@ -220,7 +220,6 @@ EclipseIO::Impl::Impl( const EclipseState& eclipseState,
 {}
 
 
-
 void EclipseIO::Impl::writeINITFile( const data::Solution& simProps, std::map<std::string, std::vector<int> > int_data, const NNC& nnc) const {
     const auto& units = this->es.getUnits();
     const IOConfig& ioConfig = this->es.cfg().io();
@@ -339,19 +338,18 @@ void EclipseIO::Impl::writeINITFile( const data::Solution& simProps, std::map<st
 
     //Write Integer Vector Map
     {
-        std::map<std::string, std::vector<int> >::iterator it = int_data.begin();
-
-        while(it != int_data.end())  {
-            std::string key = it->first;
+        for( const auto& pair : int_data)  {
+            const std::string& key = pair.first;
+            const std::vector<int>& int_data = pair.second;
             if (key.size() > ECL_STRING8_LENGTH)
-              throw std::invalid_argument("Keyword is too long.");
-            
-            std::vector<int> int_field = it->second;
-            if (int_field.size() < this->grid.getCartesianSize())
-              int_field = grid.scatterVector( int_field );
-            writeKeyword( fortio, key, int_field);
+              throw std::invalid_argument("Keyword is too long.");            
 
-            it++;
+            if (int_data.size() == this->grid.getCartesianSize( ))
+                writeKeyword( fortio , key , int_data );
+            else  {
+                std::vector<int> global_copy = grid.scatterVector( int_data );
+                writeKeyword( fortio , key , global_copy );
+            }
         }
     }
 
@@ -386,8 +384,16 @@ void EclipseIO::Impl::writeEGRIDFile( const NNC& nnc ) const {
     }
 }
 
-
-void EclipseIO::writeInitial( data::Solution simProps, std::map<std::string, std::vector<int> > map, const NNC& nnc) {
+/*
+int_data: Writes key(string) and integers vector to INIT file as eclipse keywords
+- Key: Max 8 chars.
+- vector: Size number of grid cells (N_grid = nx*ny*nz) OR number of active cells.
+    If vector size equals number of active cells, then vector is expanded to size N_grid.
+       - expanded_vector[j] = vector[i], global cell j corresponds to active cell i. 
+       - expanded_vector[j] = default (-1), if j corresponds to an inactive cell.    
+- Wrong input: invalid_argument exception.                                   
+*/
+void EclipseIO::writeInitial( data::Solution simProps, std::map<std::string, std::vector<int> > int_data, const NNC& nnc) {
     if( !this->impl->output_enabled )
         return;
 
@@ -397,7 +403,7 @@ void EclipseIO::writeInitial( data::Solution simProps, std::map<std::string, std
 
         simProps.convertFromSI( es.getUnits() );
         if( ioConfig.getWriteINITFile() )
-            this->impl->writeINITFile( simProps , map, nnc );
+            this->impl->writeINITFile( simProps , int_data, nnc );
 
         if( ioConfig.getWriteEGRIDFile( ) )
             this->impl->writeEGRIDFile( nnc );
diff --git a/tests/test_EclipseIO.cpp b/tests/test_EclipseIO.cpp
index 432e84878..9fcf7bc68 100644
--- a/tests/test_EclipseIO.cpp
+++ b/tests/test_EclipseIO.cpp
@@ -317,16 +317,14 @@ BOOST_AUTO_TEST_CASE(EclipseIOIntegration) {
             { "TRANZ", { measure::transmissibility, tranz, TargetType::INIT } },
         };
 
-        std::map<std::string, std::vector<int> > int_data;
-        std::vector<int> u(27); u[2] = 67; u[5] = 89;
-        int_data["STR_ULONGNAME"] = u;
+        std::map<std::string, std::vector<int>> int_data =  {{"STR_ULONGNAME" , {1,1,1,1,1,1,1,1} } };
 
         std::vector<int> v(27); v[2] = 67; v[26] = 89;
         int_data["STR_V"] = v;
 
         eclWriter.writeInitial( );
 
-        test_assert_throw( eclWriter.writeInitial( eGridProps , int_data) , std::invalid_argument);
+        BOOST_CHECK_THROW( eclWriter.writeInitial( eGridProps , int_data) , std::invalid_argument);
 
         int_data.erase("STR_ULONGNAME");
         eclWriter.writeInitial( eGridProps , int_data );
@@ -357,7 +355,7 @@ BOOST_AUTO_TEST_CASE(EclipseIOIntegration) {
         loadWells( "FOO.EGRID", "FOO.UNRST" );
 
         ecl_file_type * ecl_file = ecl_file_open("./FOO.INIT", 0);
-        test_assert_true( ecl_file_has_kw(ecl_file, "STR_V") );
+        BOOST_CHECK( ecl_file_has_kw(ecl_file, "STR_V") );
         ecl_kw_type * kw = ecl_file_iget_named_kw(ecl_file, "STR_V", 0);
         test_assert_double_equal(67, ecl_kw_iget_as_double(kw, 2));
         test_assert_double_equal(89, ecl_kw_iget_as_double(kw, 26));