diff --git a/wp-admin/load-scripts.php b/wp-admin/load-scripts.php
index a82088defe..f28721f7e4 100644
--- a/wp-admin/load-scripts.php
+++ b/wp-admin/load-scripts.php
@@ -15,7 +15,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 define( 'WPINC', 'wp-includes' );
 
 $protocol = $_SERVER['SERVER_PROTOCOL'];
-if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ), true ) ) {
+if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0', 'HTTP/3' ), true ) ) {
 	$protocol = 'HTTP/1.0';
 }
 
diff --git a/wp-admin/load-styles.php b/wp-admin/load-styles.php
index 84a7b729d5..fad60b7b54 100644
--- a/wp-admin/load-styles.php
+++ b/wp-admin/load-styles.php
@@ -23,7 +23,7 @@ require ABSPATH . WPINC . '/script-loader.php';
 require ABSPATH . WPINC . '/version.php';
 
 $protocol = $_SERVER['SERVER_PROTOCOL'];
-if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ), true ) ) {
+if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0', 'HTTP/3' ), true ) ) {
 	$protocol = 'HTTP/1.0';
 }
 
diff --git a/wp-comments-post.php b/wp-comments-post.php
index 06cbd460f4..e9a758dcfd 100644
--- a/wp-comments-post.php
+++ b/wp-comments-post.php
@@ -7,7 +7,7 @@
 
 if ( 'POST' !== $_SERVER['REQUEST_METHOD'] ) {
 	$protocol = $_SERVER['SERVER_PROTOCOL'];
-	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ), true ) ) {
+	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0', 'HTTP/3' ), true ) ) {
 		$protocol = 'HTTP/1.0';
 	}
 
diff --git a/wp-includes/load.php b/wp-includes/load.php
index ffbc1d2290..d2e7f47c4f 100644
--- a/wp-includes/load.php
+++ b/wp-includes/load.php
@@ -14,7 +14,7 @@
  */
 function wp_get_server_protocol() {
 	$protocol = isset( $_SERVER['SERVER_PROTOCOL'] ) ? $_SERVER['SERVER_PROTOCOL'] : '';
-	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ), true ) ) {
+	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0', 'HTTP/3' ), true ) ) {
 		$protocol = 'HTTP/1.0';
 	}
 	return $protocol;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index e81de3ec9c..864bd018d1 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-52086';
+$wp_version = '5.9-alpha-52087';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.