diff --git a/wp-admin/includes/update-core.php b/wp-admin/includes/update-core.php
index 8d672199ee..6085b02c8f 100644
--- a/wp-admin/includes/update-core.php
+++ b/wp-admin/includes/update-core.php
@@ -1431,9 +1431,13 @@ function update_core( $from, $to ) {
 		} else {
 			$lang_dir = WP_CONTENT_DIR . '/languages';
 		}
-
+		/*
+		 * Note: str_starts_with() is not used here, as this file is included
+		 * when updating from older WordPress versions, in which case
+		 * the polyfills from wp-includes/compat.php may not be available.
+		 */
 		// Check if the language directory exists first.
-		if ( ! @is_dir( $lang_dir ) && str_starts_with( $lang_dir, ABSPATH ) ) {
+		if ( ! @is_dir( $lang_dir ) && 0 === strpos( $lang_dir, ABSPATH ) ) {
 			// If it's within the ABSPATH we can handle it here, otherwise they're out of luck.
 			$wp_filesystem->mkdir( $to . str_replace( ABSPATH, '', $lang_dir ), FS_CHMOD_DIR );
 			clearstatcache(); // For FTP, need to clear the stat cache.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 5b098339a2..14a9861cd6 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56416';
+$wp_version = '6.4-alpha-56417';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.