diff --git a/CHANGELOG.md b/CHANGELOG.md
index 74c0b48..b192127 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
-## Unreleased
+## preparing 1.0.0
 
+- Use kdbx 4.x by default when creating new files.
 - Implemented support for custom icons.
 
 ## 0.4.1
diff --git a/lib/src/kdbx_format.dart b/lib/src/kdbx_format.dart
index be8f4b9..9c2fbda 100644
--- a/lib/src/kdbx_format.dart
+++ b/lib/src/kdbx_format.dart
@@ -335,7 +335,7 @@ class KdbxFormat {
     String generator,
     KdbxHeader header,
   }) {
-    header ??= KdbxHeader.createV3();
+    header ??= argon2 == null ? KdbxHeader.createV3() : KdbxHeader.createV4();
     final ctx = KdbxReadWriteContext(binaries: [], header: header);
     final meta = KdbxMeta.create(
       databaseName: name,
diff --git a/lib/src/kdbx_header.dart b/lib/src/kdbx_header.dart
index ea6f446..848447c 100644
--- a/lib/src/kdbx_header.dart
+++ b/lib/src/kdbx_header.dart
@@ -97,8 +97,23 @@ const _headerFieldsByVersion = {
   HeaderFields.ProtectedStreamKey: [KdbxVersion.V3],
   HeaderFields.StreamStartBytes: [KdbxVersion.V3],
   HeaderFields.InnerRandomStreamID: [KdbxVersion.V3],
+  HeaderFields.KdfParameters: [KdbxVersion.V4],
+  HeaderFields.PublicCustomData: [KdbxVersion.V4],
 };
 
+bool _isHeaderFieldInVersion(HeaderFields field, KdbxVersion version) {
+  final f = _headerFieldsByVersion[field];
+  if (f == null || f.isEmpty) {
+    return true;
+  }
+  for (final v in f) {
+    if (v.major == version.major) {
+      return true;
+    }
+  }
+  return false;
+}
+
 enum InnerHeaderFields {
   EndOfHeader,
   InnerRandomStreamID,
@@ -229,6 +244,10 @@ class KdbxHeader {
     // TODO make sure default algorithm is "secure" engouh. Or whether we should
     //      use like [SecureRandom] from PointyCastle?
     _setHeaderField(HeaderFields.MasterSeed, ByteUtils.randomBytes(32));
+    fields.remove(HeaderFields.TransformSeed);
+    fields.remove(HeaderFields.StreamStartBytes);
+    fields.remove(HeaderFields.ProtectedStreamKey);
+    fields.remove(HeaderFields.EncryptionIV);
     if (version.major == KdbxVersion.V3.major) {
       _setHeaderField(HeaderFields.TransformSeed, ByteUtils.randomBytes(32));
       _setHeaderField(HeaderFields.StreamStartBytes, ByteUtils.randomBytes(32));
@@ -264,6 +283,9 @@ class KdbxHeader {
     writer.writeUint16(version.major);
     for (final field
         in HeaderFields.values.where((f) => f != HeaderFields.EndOfHeader)) {
+      if (!_isHeaderFieldInVersion(field, version) && fields[field] != null) {
+        _logger.warning('Did not expect header field $field in $version');
+      }
       _writeField(writer, field);
     }
     fields[HeaderFields.EndOfHeader] =
@@ -338,9 +360,9 @@ class KdbxHeader {
         HeaderFields.CompressionFlags:
             WriterHelper.singleUint32Bytes(Compression.gzip.id),
         HeaderFields.KdfParameters: _createKdfDefaultParameters().write(),
-        HeaderFields.InnerRandomStreamID: WriterHelper.singleUint32Bytes(
-            ProtectedValueEncryption.values
-                .indexOf(ProtectedValueEncryption.chaCha20)),
+//        HeaderFields.InnerRandomStreamID: WriterHelper.singleUint32Bytes(
+//            ProtectedValueEncryption.values
+//                .indexOf(ProtectedValueEncryption.chaCha20)),
       });
 
   static Map<HeaderFields, HeaderField> _headerFields(
@@ -483,8 +505,10 @@ class KdbxHeader {
       _logger.fine('Creating kdf parameters.');
       writeKdfParameters(_createKdfDefaultParameters());
     }
-    _setHeaderField(
-        HeaderFields.InnerRandomStreamID,
+    fields.remove(HeaderFields.TransformRounds);
+    fields.remove(HeaderFields.InnerRandomStreamID);
+    _setInnerHeaderField(
+        InnerHeaderFields.InnerRandomStreamID,
         WriterHelper.singleUint32Bytes(ProtectedValueEncryption.values
             .indexOf(ProtectedValueEncryption.chaCha20)));
   }
diff --git a/lib/src/kdbx_xml.dart b/lib/src/kdbx_xml.dart
index 16bad8b..4503a85 100644
--- a/lib/src/kdbx_xml.dart
+++ b/lib/src/kdbx_xml.dart
@@ -58,9 +58,16 @@ abstract class KdbxSubNode<T> {
   void set(T value);
 
   void remove() {
-    for (final el in node.node.findElements(name)) {
-      el.parentElement.children.remove(el);
-    }
+    node.modify(() {
+      node.node.children.removeElementsByName(name);
+    });
+  }
+}
+
+extension on List<XmlNode> {
+  void removeElementsByName(String name) {
+    removeWhere(
+        (element) => element is XmlElement && element.name.local == name);
   }
 }
 
diff --git a/test/internal/test_utils.dart b/test/internal/test_utils.dart
index ee1d0f5..12735af 100644
--- a/test/internal/test_utils.dart
+++ b/test/internal/test_utils.dart
@@ -4,9 +4,6 @@ import 'dart:typed_data';
 
 import 'package:argon2_ffi_base/argon2_ffi_base.dart';
 import 'package:kdbx/kdbx.dart';
-
-// ignore_for_file: non_constant_identifier_names
-
 import 'package:logging/logging.dart';
 
 final _logger = Logger('test_utils');
@@ -48,4 +45,11 @@ class TestUtil {
     return await readKdbxFileBytes(await file.save(),
         credentials: file.credentials);
   }
+
+  static Future<void> saveTestOutput(String name, KdbxFile file) async {
+    final bytes = await file.save();
+    final outFile = File('test_output_$name.kdbx');
+    await outFile.writeAsBytes(bytes);
+    _logger.info('Written to $outFile');
+  }
 }
diff --git a/test/kdbx_history_test.dart b/test/kdbx_history_test.dart
index f9171bc..5df2dac 100644
--- a/test/kdbx_history_test.dart
+++ b/test/kdbx_history_test.dart
@@ -57,7 +57,7 @@ void main() {
       final dirtyExpect = StreamExpect(file.dirtyObjectsChanged);
       {
         final first = file.body.rootGroup.entries.first;
-        expect(file.header.versionMajor, 3);
+        expect(file.header.version.major, 3);
         expect(first.getString(TestUtil.keyTitle).getText(), valueOrig);
         await dirtyExpect.expectNext({first}, () {
           first.setString(TestUtil.keyTitle, PlainValue(value1));
diff --git a/test/kdbx_upgrade_test.dart b/test/kdbx_upgrade_test.dart
new file mode 100644
index 0000000..4f6c4ee
--- /dev/null
+++ b/test/kdbx_upgrade_test.dart
@@ -0,0 +1,21 @@
+import 'package:kdbx/src/kdbx_header.dart';
+import 'package:logging_appenders/logging_appenders.dart';
+import 'package:test/test.dart';
+
+import 'internal/test_utils.dart';
+
+void main() {
+  PrintAppender.setupLogging();
+  group('Test upgrade from v3 to v4', () {
+    final format = TestUtil.kdbxFormat();
+    test('Read v3, write v4', () async {
+      final file =
+          await TestUtil.readKdbxFile('test/FooBar.kdbx', password: 'FooBar');
+      expect(file.header.version, KdbxVersion.V3_1);
+      file.upgrade(KdbxVersion.V4.major);
+      final v4 = await TestUtil.saveAndRead(file);
+      expect(v4.header.version, KdbxVersion.V4);
+      await TestUtil.saveTestOutput('kdbx4upgrade', v4);
+    });
+  });
+}