diff --git a/wp-includes/rest-api/class-wp-rest-request.php b/wp-includes/rest-api/class-wp-rest-request.php
index 7c8d189906..87689a94a5 100644
--- a/wp-includes/rest-api/class-wp-rest-request.php
+++ b/wp-includes/rest-api/class-wp-rest-request.php
@@ -957,6 +957,7 @@ class WP_REST_Request implements ArrayAccess {
 	 * @param string $offset Parameter name.
 	 * @return bool Whether the parameter is set.
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetExists( $offset ) {
 		$order = $this->get_parameter_order();
 
@@ -977,6 +978,7 @@ class WP_REST_Request implements ArrayAccess {
 	 * @param string $offset Parameter name.
 	 * @return mixed|null Value if set, null otherwise.
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetGet( $offset ) {
 		return $this->get_param( $offset );
 	}
@@ -989,6 +991,7 @@ class WP_REST_Request implements ArrayAccess {
 	 * @param string $offset Parameter name.
 	 * @param mixed  $value  Parameter value.
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetSet( $offset, $value ) {
 		$this->set_param( $offset, $value );
 	}
@@ -1000,6 +1003,7 @@ class WP_REST_Request implements ArrayAccess {
 	 *
 	 * @param string $offset Parameter name.
 	 */
+	#[ReturnTypeWillChange]
 	public function offsetUnset( $offset ) {
 		$order = $this->get_parameter_order();
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 609c53073e..01f1b12f9f 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51530';
+$wp_version = '5.9-alpha-51531';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.