diff --git a/lib/src/date_picker_theme.dart b/lib/src/date_picker_theme.dart
index 08bfffc..308d70c 100644
--- a/lib/src/date_picker_theme.dart
+++ b/lib/src/date_picker_theme.dart
@@ -1,5 +1,5 @@
-import 'package:flutter/material.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
 
 /// Default value of DatePicker's background color.
 const DATETIME_PICKER_BACKGROUND_COLOR = Colors.white;
@@ -20,7 +20,7 @@ const double DATETIME_PICKER_ITEM_HEIGHT = 36.0;
 const TextStyle DATETIME_PICKER_ITEM_TEXT_STYLE =
     const TextStyle(color: Color(0xFF000046), fontSize: 16.0);
 
-class DateTimePickerTheme with DiagnosticableMixin {
+class DateTimePickerTheme with DiagnosticableTreeMixin {
   final cancelDefault = const Text('OK');
 
   /// DateTimePicker theme.