diff --git a/wp-includes/class-wp-theme-json-data.php b/wp-includes/class-wp-theme-json-data.php
index 089e65eddb..9ffa2f3585 100644
--- a/wp-includes/class-wp-theme-json-data.php
+++ b/wp-includes/class-wp-theme-json-data.php
@@ -10,6 +10,7 @@
 /**
  * Class to provide access to update a theme.json structure.
  */
+#[AllowDynamicProperties]
 class WP_Theme_JSON_Data {
 
 	/**
diff --git a/wp-includes/style-engine/class-wp-style-engine-css-declarations.php b/wp-includes/style-engine/class-wp-style-engine-css-declarations.php
index 0b9eb59a15..23efd6a40c 100644
--- a/wp-includes/style-engine/class-wp-style-engine-css-declarations.php
+++ b/wp-includes/style-engine/class-wp-style-engine-css-declarations.php
@@ -16,6 +16,7 @@
  *
  * @since 6.1.0
  */
+#[AllowDynamicProperties]
 class WP_Style_Engine_CSS_Declarations {
 
 	/**
diff --git a/wp-includes/style-engine/class-wp-style-engine-css-rule.php b/wp-includes/style-engine/class-wp-style-engine-css-rule.php
index 6e53418121..53225d7d65 100644
--- a/wp-includes/style-engine/class-wp-style-engine-css-rule.php
+++ b/wp-includes/style-engine/class-wp-style-engine-css-rule.php
@@ -16,6 +16,7 @@
  *
  * @since 6.1.0
  */
+#[AllowDynamicProperties]
 class WP_Style_Engine_CSS_Rule {
 
 	/**
diff --git a/wp-includes/style-engine/class-wp-style-engine-css-rules-store.php b/wp-includes/style-engine/class-wp-style-engine-css-rules-store.php
index 9b1ed7e706..235fe53e92 100644
--- a/wp-includes/style-engine/class-wp-style-engine-css-rules-store.php
+++ b/wp-includes/style-engine/class-wp-style-engine-css-rules-store.php
@@ -16,6 +16,7 @@
  *
  * @since 6.1.0
  */
+#[AllowDynamicProperties]
 class WP_Style_Engine_CSS_Rules_Store {
 
 	/**
diff --git a/wp-includes/style-engine/class-wp-style-engine-processor.php b/wp-includes/style-engine/class-wp-style-engine-processor.php
index 8e035b59ee..241437b204 100644
--- a/wp-includes/style-engine/class-wp-style-engine-processor.php
+++ b/wp-includes/style-engine/class-wp-style-engine-processor.php
@@ -16,6 +16,7 @@
  *
  * @since 6.1.0
  */
+#[AllowDynamicProperties]
 class WP_Style_Engine_Processor {
 
 	/**
diff --git a/wp-includes/style-engine/class-wp-style-engine.php b/wp-includes/style-engine/class-wp-style-engine.php
index c6554c5dd9..951dac4b54 100644
--- a/wp-includes/style-engine/class-wp-style-engine.php
+++ b/wp-includes/style-engine/class-wp-style-engine.php
@@ -21,6 +21,7 @@
  * @access private
  * @since 6.1.0
  */
+#[AllowDynamicProperties]
 final class WP_Style_Engine {
 	/**
 	 * Style definitions that contain the instructions to
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 4f19591b86..55fa82bb29 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-beta3-54480';
+$wp_version = '6.1-beta3-54481';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.