diff --git a/core/kernel/persistence/starsql/class.StarIterator.php b/core/kernel/persistence/starsql/class.StarIterator.php
index b96401296..77255440c 100644
--- a/core/kernel/persistence/starsql/class.StarIterator.php
+++ b/core/kernel/persistence/starsql/class.StarIterator.php
@@ -15,7 +15,7 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  *
- * Copyright (c) 2002-2008 (original work) 2014 Open Assessment Technologies SA
+ * Copyright (c) 2023 (original work) Open Assessment Technologies SA
  *
  */
 
@@ -26,8 +26,6 @@
 /**
  * Iterator over all triples
  *
- * @author joel bout <joel@taotesting.com>
- * @package generis
  */
 class core_kernel_persistence_starsql_StarIterator extends \IteratorIterator implements \RecursiveIterator
 {
diff --git a/core/kernel/persistence/starsql/class.StarRdf.php b/core/kernel/persistence/starsql/class.StarRdf.php
index bd0443edc..1ac072b17 100644
--- a/core/kernel/persistence/starsql/class.StarRdf.php
+++ b/core/kernel/persistence/starsql/class.StarRdf.php
@@ -152,8 +152,10 @@ private function createSystemTripleQuery(iterable $tripleList): ?Statement
             $query = Query::new()->match($systemNode)
                 ->where($systemNode->property('uri')->in(array_keys($systemSubjectList)))
                 ->set($systemNode->labeled('System'));
+
+            $query = Statement::create($query->build());
         }
 
-        return Statement::create($query->build());
+        return $query;
     }
 }
diff --git a/test/unit/core/data/import/RdfImportTest.php b/test/unit/core/data/import/RdfImportTest.php
index 8bf6bec64..23411f520 100644
--- a/test/unit/core/data/import/RdfImportTest.php
+++ b/test/unit/core/data/import/RdfImportTest.php
@@ -34,8 +34,8 @@ class RdfImportTest extends GenerisTestCase
     public function testRdfTripleImport(Ontology $ontology)
     {
         $this->assertEquals(0, $this->getTripleCount($ontology));
-        $triple1 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object');
-        $triple2 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object2');
+        $triple1 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object');
+        $triple2 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object2');
         $importer = new RdfImporter();
         $importer->setServiceLocator($ontology->getServiceLocator());
         $importer->importTriples([$triple1, $triple2]);
diff --git a/test/unit/core/kernel/persistence/OntologyRdfTest.php b/test/unit/core/kernel/persistence/OntologyRdfTest.php
index f7ef03104..615af062b 100644
--- a/test/unit/core/kernel/persistence/OntologyRdfTest.php
+++ b/test/unit/core/kernel/persistence/OntologyRdfTest.php
@@ -38,8 +38,8 @@ class OntologyRdfTest extends GenerisTestCase
     public function testRdfInterface(Ontology $ontology)
     {
         $this->assertEquals(0, $this->getTripleCount($ontology));
-        $triple1 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object');
-        $triple2 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object2');
+        $triple1 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object');
+        $triple2 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object2');
         $ontology->getRdfInterface()->add($triple1);
         $this->assertEquals(1, $this->getTripleCount($ontology));
         $ontology->getRdfInterface()->remove($triple2);
@@ -55,7 +55,7 @@ public function testRdfInterface(Ontology $ontology)
     public function testAdd(Ontology $ontology)
     {
         $this->assertEquals(0, $this->getTripleCount($ontology));
-        $triple1 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object');
+        $triple1 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object');
         $ontology->getRdfInterface()->add($triple1);
         $this->assertEquals(1, $this->getTripleCount($ontology));
         $triples = $ontology->getRdfInterface();
@@ -79,9 +79,9 @@ public function testAddTripleCollection(Ontology $ontology)
         $this->assertInstanceOf(Ontology::class, $ontology);
         $this->assertEquals(0, $this->getTripleCount($ontology));
 
-        $triple1 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object');
-        $triple2 = core_kernel_classes_Triple::createTriple(0, 'subject2', OntologyRdf::RDF_TYPE, 'object2');
-        $triple3 = core_kernel_classes_Triple::createTriple(0, 'subject3', OntologyRdfs::RDFS_SUBCLASSOF, 'object2');
+        $triple1 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object');
+        $triple2 = core_kernel_classes_Triple::createTriple(2, 'subject2', OntologyRdf::RDF_TYPE, 'object2');
+        $triple3 = core_kernel_classes_Triple::createTriple(2, 'subject3', OntologyRdfs::RDFS_SUBCLASSOF, 'object2');
         $ontology->getRdfInterface()->addTripleCollection([$triple1, $triple2, $triple3]);
 
         $this->assertEquals(3, $this->getTripleCount($ontology));
@@ -95,7 +95,7 @@ public function testRemove(Ontology $ontology)
     {
         $this->assertInstanceOf(Ontology::class, $ontology);
         $this->assertEquals(0, $this->getTripleCount($ontology));
-        $triple1 = core_kernel_classes_Triple::createTriple(0, 'subject', 'predicate', 'object');
+        $triple1 = core_kernel_classes_Triple::createTriple(2, 'subject', 'predicate', 'object');
         $ontology->getRdfInterface()->add($triple1);
         $this->assertEquals(1, $this->getTripleCount($ontology));
         $ontology->getRdfInterface()->remove($triple1);