diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 721a83792b..0eed46017e 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -79,6 +79,7 @@ Changelog
  * Replace latin abbreviations (i.e. / e.g.) with common English phrases so that documentation is easier to understand (Dominik Lech)
  * Add shortcut for accessing StreamField blocks by block name with new `blocks_by_name` and `first_block_by_name` methods on `StreamValue` (Tidiane Dia, Matt Westcott)
  * Extend support for custom user interface colours across almost all admin colours (Thibaud Colas)
+ * Add HTML-aware max_length validation on RichTextField and RichTextBlock (Matt Westcott)
  * Fix: Typo in `ResumeWorkflowActionFormatter` message (Stefan Hammer)
  * Fix: Throw a meaningful error when saving an image to an unrecognised image format (Christian Franke)
  * Fix: Remove extra padding for headers with breadcrumbs on mobile viewport (Steven Steinwand)
diff --git a/docs/releases/4.0.md b/docs/releases/4.0.md
index a95c71f97a..c1ee3b6fa8 100644
--- a/docs/releases/4.0.md
+++ b/docs/releases/4.0.md
@@ -102,6 +102,7 @@ In Wagtail 2.12, we introduced theming support for Wagtail’s primary brand col
  * Improve help block styles in Windows High Contrast Mode with less reliance on communication via colour alone (Anuja Verma)
  * Replace latin abbreviations (i.e. / e.g.) with common English phrases so that documentation is easier to understand (Dominik Lech)
  * Add shortcut for accessing StreamField blocks by block name with new [`blocks_by_name` and `first_block_by_name` methods on `StreamValue`](streamfield_retrieving_blocks_by_name) (Tidiane Dia, Matt Westcott)
+ * Add HTML-aware max_length validation on RichTextField and RichTextBlock (Matt Westcott)
 
 ### Bug fixes