diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5e98d6b..8799159 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 4.0.1
+
+* Fix error that it can't find File.length() method at web.
+
 ## 4.0.0
 
 * Migrate to 3.16.0
diff --git a/lib/src/_platform_web.dart b/lib/src/_platform_web.dart
index dc98a52..8d7b829 100644
--- a/lib/src/_platform_web.dart
+++ b/lib/src/_platform_web.dart
@@ -22,6 +22,13 @@ class File {
   /// is the contents of the file.
   Future<Uint8List> readAsBytes() async => Uint8List.fromList(<int>[]);
 
+  /// The length of the file.
+  ///
+  /// Returns a `Future<int>` that completes with the length in bytes.
+  Future<int> length() async {
+    return 0;
+  }
+
   /// The path of the file underlying this random access file.
   final String path;
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index 1192404..960443a 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: extended_image_library
 description: package library for extended_image, extended_text and extended_text_field, provide common base class.
-version: 4.0.0
+version: 4.0.1
 homepage: https://github.com/fluttercandies/extended_image_library
 
 environment: