diff --git a/python/core/qgsdefaultvalue.sip b/python/core/qgsdefaultvalue.sip
index 196affe9ac6..9ca357c323b 100644
--- a/python/core/qgsdefaultvalue.sip
+++ b/python/core/qgsdefaultvalue.sip
@@ -38,7 +38,7 @@ not set, the default value will only be used when a feature is created.
 %End
   public:
 
-    QgsDefaultValue( const QString &expression = QString(), bool applyOnUpdate = false );
+    explicit QgsDefaultValue( const QString &expression = QString(), bool applyOnUpdate = false );
 %Docstring
 Create a new default value with the given ``expression`` and ``applyOnUpdate`` flag.
 
diff --git a/src/app/qgsattributesformproperties.cpp b/src/app/qgsattributesformproperties.cpp
index 7136535eb1b..966ac250a56 100644
--- a/src/app/qgsattributesformproperties.cpp
+++ b/src/app/qgsattributesformproperties.cpp
@@ -242,7 +242,6 @@ void QgsAttributesFormProperties::loadAttributeTypeDialog()
     mAttributeTypeDialog->setConstraintExpressionEnforced( cfg.mConstraintStrength.value( QgsFieldConstraints::ConstraintExpression, QgsFieldConstraints::ConstraintStrengthHard ) == QgsFieldConstraints::ConstraintStrengthHard );
     mAttributeTypeDialog->setDefaultValueExpression( mLayer->defaultValueDefinition( index ).expression() );
     mAttributeTypeDialog->setApplyDefaultValueOnUpdate( mLayer->defaultValueDefinition( index ).applyOnUpdate() );
-    //confustion (will be removed): das hier funktioniert nicht, es is neu, aber ich weiss nicht woher: mAttributeTypeDialog->setDefaultValueExpression( mLayer->defaultValueExpression( index ) );
 
     mAttributeTypeDialog->setEditorWidgetConfig( cfg.mEditorWidgetConfig );
     mAttributeTypeDialog->setEditorWidgetType( cfg.mEditorWidgetType );
diff --git a/src/core/qgsdefaultvalue.h b/src/core/qgsdefaultvalue.h
index fcba410ca06..c7000426e27 100644
--- a/src/core/qgsdefaultvalue.h
+++ b/src/core/qgsdefaultvalue.h
@@ -57,7 +57,7 @@ class CORE_EXPORT QgsDefaultValue
      * Create a new default value with the given \a expression and \a applyOnUpdate flag.
      * \see QgsVectorLayer::setDefaultValueDefinition
      */
-    QgsDefaultValue( const QString &expression = QString(), bool applyOnUpdate = false );
+    explicit QgsDefaultValue( const QString &expression = QString(), bool applyOnUpdate = false );
     bool operator==( const QgsDefaultValue &other ) const;
 
     /**
diff --git a/src/core/qgsvectorlayer.cpp b/src/core/qgsvectorlayer.cpp
index 6f500bffbc4..ca250cecb7a 100644
--- a/src/core/qgsvectorlayer.cpp
+++ b/src/core/qgsvectorlayer.cpp
@@ -3159,9 +3159,9 @@ void QgsVectorLayer::setDefaultValueDefinition( int index, const QgsDefaultValue
 QgsDefaultValue QgsVectorLayer::defaultValueDefinition( int index ) const
 {
   if ( index < 0 || index >= mFields.count() )
-    return QString();
+    return QgsDefaultValue();
   else
-    return mFields.at( index ).defaultValueDefinition().expression();
+    return mFields.at( index ).defaultValueDefinition();
 }
 
 QSet<QVariant> QgsVectorLayer::uniqueValues( int index, int limit ) const
diff --git a/tests/src/core/testqgsfield.cpp b/tests/src/core/testqgsfield.cpp
index b5795f14ef5..2f6de8f25c8 100644
--- a/tests/src/core/testqgsfield.cpp
+++ b/tests/src/core/testqgsfield.cpp
@@ -135,7 +135,7 @@ void TestQgsField::gettersSetters()
   QCOMPARE( field.comment(), QString( "comment" ) );
   field.setAlias( QStringLiteral( "alias" ) );
   QCOMPARE( field.alias(), QString( "alias" ) );
-  field.setDefaultValueDefinition( QStringLiteral( "1+2" ) );
+  field.setDefaultValueDefinition( QgsDefaultValue( QStringLiteral( "1+2" ) ) );
   QCOMPARE( field.defaultValueDefinition().expression(), QString( "1+2" ) );
   QgsFieldConstraints constraints;
   constraints.setConstraint( QgsFieldConstraints::ConstraintNotNull, QgsFieldConstraints::ConstraintOriginProvider );
@@ -244,10 +244,10 @@ void TestQgsField::equality()
   QVERIFY( !( field1 == field2 ) );
   QVERIFY( field1 != field2 );
   field2.setAlias( QString() );
-  field2.setDefaultValueDefinition( QStringLiteral( "1+2" ) );
+  field2.setDefaultValueDefinition( QgsDefaultValue( QStringLiteral( "1+2" ) ) );
   QVERIFY( !( field1 == field2 ) );
   QVERIFY( field1 != field2 );
-  field2.setDefaultValueDefinition( QString() );
+  field2.setDefaultValueDefinition( QgsDefaultValue() );
   constraints = field2.constraints();
   constraints.removeConstraint( QgsFieldConstraints::ConstraintNotNull );
   field2.setConstraints( constraints );
@@ -461,7 +461,7 @@ void TestQgsField::dataStream()
   original.setTypeName( QStringLiteral( "typename1" ) );
   original.setComment( QStringLiteral( "comment1" ) );
   original.setAlias( QStringLiteral( "alias" ) );
-  original.setDefaultValueDefinition( QStringLiteral( "default" ) );
+  original.setDefaultValueDefinition( QgsDefaultValue( QStringLiteral( "default" ) ) );
   QgsFieldConstraints constraints;
   constraints.setConstraint( QgsFieldConstraints::ConstraintNotNull, QgsFieldConstraints::ConstraintOriginProvider );
   constraints.setConstraint( QgsFieldConstraints::ConstraintUnique, QgsFieldConstraints::ConstraintOriginLayer );
diff --git a/tests/src/python/test_qgsvectorlayer.py b/tests/src/python/test_qgsvectorlayer.py
index 568899971c6..d5a819cb290 100755
--- a/tests/src/python/test_qgsvectorlayer.py
+++ b/tests/src/python/test_qgsvectorlayer.py
@@ -2061,14 +2061,28 @@ class TestQgsVectorLayer(unittest.TestCase, FeatureSourceTestCase):
         layer.setDefaultValueDefinition(0, QgsDefaultValue("'test'"))
         self.assertTrue(layer.defaultValueDefinition(0))
         self.assertEqual(layer.defaultValueDefinition(0).expression(), "'test'")
+        self.assertFalse(layer.defaultValueDefinition(0).applyOnUpdate())
         self.assertFalse(layer.defaultValueDefinition(1))
+        self.assertFalse(layer.defaultValueDefinition(1).applyOnUpdate())
         self.assertFalse(layer.defaultValueDefinition(2))
+        self.assertFalse(layer.defaultValueDefinition(2).applyOnUpdate())
         self.assertEqual(layer.fields().at(0).defaultValueDefinition().expression(), "'test'")
 
         layer.setDefaultValueDefinition(1, QgsDefaultValue("2+2"))
         self.assertEqual(layer.defaultValueDefinition(0).expression(), "'test'")
+        self.assertFalse(layer.defaultValueDefinition(0).applyOnUpdate())
         self.assertEqual(layer.defaultValueDefinition(1).expression(), "2+2")
+        self.assertFalse(layer.defaultValueDefinition(1).applyOnUpdate())
         self.assertFalse(layer.defaultValueDefinition(2))
+        self.assertFalse(layer.defaultValueDefinition(2).applyOnUpdate())
+        self.assertEqual(layer.fields().at(0).defaultValueDefinition().expression(), "'test'")
+        self.assertEqual(layer.fields().at(1).defaultValueDefinition().expression(), "2+2")
+
+        layer.setDefaultValueDefinition(1, QgsDefaultValue("2+2", True))
+        self.assertEqual(layer.defaultValueDefinition(0).expression(), "'test'")
+        self.assertFalse(layer.defaultValueDefinition(0).applyOnUpdate())
+        self.assertEqual(layer.defaultValueDefinition(1).expression(), "2+2")
+        self.assertTrue(layer.defaultValueDefinition(1).applyOnUpdate())
         self.assertEqual(layer.fields().at(0).defaultValueDefinition().expression(), "'test'")
         self.assertEqual(layer.fields().at(1).defaultValueDefinition().expression(), "2+2")
 
diff --git a/tests/testdata/polys_overlapping_with_id.dbf b/tests/testdata/polys_overlapping_with_id.dbf
index fd276803f68..775d4ad0421 100644
Binary files a/tests/testdata/polys_overlapping_with_id.dbf and b/tests/testdata/polys_overlapping_with_id.dbf differ