diff --git a/wp-includes/class-wp-theme.php b/wp-includes/class-wp-theme.php
index a72035331f..dba5cb3d6b 100644
--- a/wp-includes/class-wp-theme.php
+++ b/wp-includes/class-wp-theme.php
@@ -21,6 +21,8 @@ final class WP_Theme implements ArrayAccess {
 	/**
 	 * Headers for style.css files.
 	 *
+	 * @since 3.4.0
+	 * @since 5.4.0 Added `Requires at least` and `Requires PHP` headers.
 	 * @var array
 	 */
 	private static $file_headers = array(
@@ -35,6 +37,8 @@ final class WP_Theme implements ArrayAccess {
 		'Tags'        => 'Tags',
 		'TextDomain'  => 'Text Domain',
 		'DomainPath'  => 'Domain Path',
+		'RequiresWP'  => 'Requires at least',
+		'RequiresPHP' => 'Requires PHP',
 	);
 
 	/**
@@ -801,11 +805,13 @@ final class WP_Theme implements ArrayAccess {
 	 * Sanitize a theme header.
 	 *
 	 * @since 3.4.0
+	 * @since 5.4.0 Added support for `Requires at least` and `Requires PHP` headers.
 	 *
 	 * @staticvar array $header_tags
 	 * @staticvar array $header_tags_with_a
 	 *
-	 * @param string $header Theme header. Name, Description, Author, Version, ThemeURI, AuthorURI, Status, Tags.
+	 * @param string $header Theme header. Accepts 'Name', 'Description', 'Author', 'Version',
+	 *                       'ThemeURI', 'AuthorURI', 'Status', 'Tags', 'RequiresWP', 'RequiresPHP'.
 	 * @param string $value  Value to sanitize.
 	 * @return string|array An array for Tags header, string otherwise.
 	 */
@@ -853,6 +859,8 @@ final class WP_Theme implements ArrayAccess {
 				$value = array_filter( array_map( 'trim', explode( ',', strip_tags( $value ) ) ) );
 				break;
 			case 'Version':
+			case 'RequiresWP':
+			case 'RequiresPHP':
 				$value = strip_tags( $value );
 				break;
 		}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 2505788971..ff8e6678f2 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.4-alpha-47144';
+$wp_version = '5.4-alpha-47145';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.