diff --git a/CHANGELOG.md b/CHANGELOG.md
index b1f6405..7a9a38f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+* Fixed that transformer hook function might also return `null`.
+
 ## [0.2.1] - 2024-11-16
 
 ### Added
diff --git a/README.md b/README.md
index 023e5c2..2e12c7a 100644
--- a/README.md
+++ b/README.md
@@ -100,6 +100,12 @@ We're always interested in your feedback. Feel free to reach out to us via [E-Ma
 
 ## Changelog ##
 
+## Unreleased
+
+### Fixed
+
+* Fixed that transformer hook function might also return `null`.
+
 ### [0.2.1] 2024-11-16 ###
 
 * Initial release on https://wordpress.org/