diff --git a/user_guide_src/source/changelogs/v4.3.7.rst b/user_guide_src/source/changelogs/v4.3.7.rst
index 47fc19f161d1..7bb8ba84b9e2 100644
--- a/user_guide_src/source/changelogs/v4.3.7.rst
+++ b/user_guide_src/source/changelogs/v4.3.7.rst
@@ -15,6 +15,9 @@ BREAKING
 - **FeatureTestTrait:** When using :ref:`withBodyFormat() <feature-formatting-the-request>`,
   the priority of the request body has been changed.
   See :ref:`Upgrading Guide <upgrade-437-feature-testing>` for details.
+- **Validation:** The return value of ``Validation::loadRuleGroup()`` has been
+  changed from "**rules array**" to "**array** of **rules array** and **customErrors array**"
+  (``[rules, customErrors]``).
 
 Message Changes
 ***************
diff --git a/user_guide_src/source/installation/upgrade_437.rst b/user_guide_src/source/installation/upgrade_437.rst
index 389c145f4109..cc3e38fd030d 100644
--- a/user_guide_src/source/installation/upgrade_437.rst
+++ b/user_guide_src/source/installation/upgrade_437.rst
@@ -39,6 +39,19 @@ is not used::
 
 Previously, the ``$body`` was used for the request body.
 
+Return value of Validation::loadRuleGroup()
+===========================================
+
+The return value of ``Validation::loadRuleGroup()`` has been changed from
+"**rules array**" to "**array** of **rules array** and **customErrors array**"
+(``[rules, customErrors]``).
+
+If you use the method, update the code like the following::
+
+    $rules = $this->validation->loadRuleGroup($rules);
+        ↓
+    [$rules, $customErrors] = $this->validation->loadRuleGroup($rules);
+
 Breaking Enhancements
 *********************