diff --git a/lib/src/kdbx_file.dart b/lib/src/kdbx_file.dart
index 16b3885..7eae5aa 100644
--- a/lib/src/kdbx_file.dart
+++ b/lib/src/kdbx_file.dart
@@ -151,6 +151,13 @@ class KdbxFile {
         ? header.upgradeMinor(majorVersion, minorVersion)
         : header.upgrade(majorVersion, minorVersion);
 
+    // Do this even we were already in v4.x since some KDBX software (including
+    // earlier versions of Kee Vault) skipped this step when upgrading from <v4.
+    // One probably won't call this upgrade function unless the version is <4.1
+    // so if there are some 4.1 files with this problem, they won't be fixed.
+    // If that happens we could develop a "force upgrade" feature in the
+    // user-facing software (such as Kee Vault) and tell users to activate that
+    // in order to fix export compatibility with strict clients like KeePass.
     upgradeDateTimeFormatV4();
 
     body.meta.settingsChanged.setToNow();
diff --git a/pubspec.yaml b/pubspec.yaml
index 17ceefd..659eab2 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: kdbx
 description: KeepassX format implementation in pure dart. (kdbx 3.x and 4.x support).
-version: 0.6.0+3
+version: 0.6.0+4
 homepage: https://github.com/kee-org/kdbx.dart
 publish_to: none
 
diff --git a/test/kdbx_upgrade_test.dart b/test/kdbx_upgrade_test.dart
index e90b790..a6ecc9c 100644
--- a/test/kdbx_upgrade_test.dart
+++ b/test/kdbx_upgrade_test.dart
@@ -1,4 +1,3 @@
-
 import 'package:kdbx/kdbx.dart';
 import 'package:kdbx/src/internal/extension_utils.dart';
 import 'package:kdbx/src/kdbx_xml.dart';
@@ -37,6 +36,7 @@ void main() {
       file.upgrade(KdbxVersion.V4.major, 1);
       final v4 = await TestUtil.saveAndRead(file);
       expect(v4.header.version, KdbxVersion.V4_1);
+      checkDateValues(v4);
       await TestUtil.saveTestOutput('kdbx4upgrade4-41', v4);
     }, tags: 'kdbx4');
 
@@ -53,30 +53,49 @@ void main() {
       file.upgrade(KdbxVersion.V4.major, 1);
       final v4 = await TestUtil.saveAndRead(await TestUtil.saveAndRead(file));
       expect(v4.header.version, KdbxVersion.V4_1);
+      checkDateValues(v4);
+    }, tags: 'kdbx4');
 
-      final metaValues = [
-        v4.body.meta.node.singleElement('DatabaseNameChanged')?.text,
-        v4.body.meta.node.singleElement('DatabaseDescriptionChanged')?.text,
-        v4.body.meta.node.singleElement('DefaultUserNameChanged')?.text,
-        v4.body.meta.node.singleElement('MasterKeyChanged')?.text,
-        v4.body.meta.node.singleElement('RecycleBinChanged')?.text,
-        v4.body.meta.node.singleElement('EntryTemplatesGroupChanged')?.text,
-        v4.body.meta.node.singleElement('SettingsChanged')?.text,
-      ];
-      metaValues.forEach(checkIsBase64Date);
+    test('Forced upgrade from v4.1 with bad dates transforms date format',
+        () async {
+      final file = await TestUtil.readKdbxFile(
+          'test/test_files/v4_1-invalid-dates.kdbx',
+          password: 'asdf');
+      expect(file.header.version, KdbxVersion.V4_1);
+      file.upgrade(KdbxVersion.V4.major, 1);
+      final v4 = await TestUtil.saveAndRead(await TestUtil.saveAndRead(file));
+      expect(v4.header.version, KdbxVersion.V4_1);
+      checkDateValues(v4);
+    }, tags: 'kdbx4');
 
-      v4.body.rootGroup
-          .getAllEntries()
-          .values
-          .forEach(checkObjectHasBase64Dates);
-      v4.body.rootGroup
-          .getAllGroups()
-          .values
-          .forEach(checkObjectHasBase64Dates);
+    test('Upgrade from v4.0 with good dates', () async {
+      final file = await TestUtil.readKdbxFile('test/test_files/v4.0.kdbx',
+          password: 'FooBar');
+      expect(file.header.version, KdbxVersion.V4);
+      file.upgrade(KdbxVersion.V4.major, 1);
+      final v4 = await TestUtil.saveAndRead(await TestUtil.saveAndRead(file));
+      expect(v4.header.version, KdbxVersion.V4_1);
+      checkDateValues(v4);
     }, tags: 'kdbx4');
   }, tags: ['kdbx4']);
 }
 
+void checkDateValues(KdbxFile v4) {
+  final metaValues = [
+    v4.body.meta.node.singleElement('DatabaseNameChanged')?.text,
+    v4.body.meta.node.singleElement('DatabaseDescriptionChanged')?.text,
+    v4.body.meta.node.singleElement('DefaultUserNameChanged')?.text,
+    v4.body.meta.node.singleElement('MasterKeyChanged')?.text,
+    v4.body.meta.node.singleElement('RecycleBinChanged')?.text,
+    v4.body.meta.node.singleElement('EntryTemplatesGroupChanged')?.text,
+    v4.body.meta.node.singleElement('SettingsChanged')?.text,
+  ];
+  metaValues.forEach(checkIsBase64Date);
+
+  v4.body.rootGroup.getAllEntries().values.forEach(checkObjectHasBase64Dates);
+  v4.body.rootGroup.getAllGroups().values.forEach(checkObjectHasBase64Dates);
+}
+
 // Sometimes the nodes can contain an XmlNodeList with a single element, rather than directly containing an XmlText node. Bug in XML lib?
 // Have to work around by using deprecated text property which works no matter which approach the library decides to take this time.
 void checkObjectHasBase64Dates(KdbxObject? obj) {
diff --git a/test/test_files/v4.0.kdbx b/test/test_files/v4.0.kdbx
new file mode 100644
index 0000000..9c0724b
Binary files /dev/null and b/test/test_files/v4.0.kdbx differ
diff --git a/test/test_files/v4_1-invalid-dates.kdbx b/test/test_files/v4_1-invalid-dates.kdbx
new file mode 100644
index 0000000..fa5d919
Binary files /dev/null and b/test/test_files/v4_1-invalid-dates.kdbx differ