diff --git a/wp-admin/includes/class-wp-upgrader.php b/wp-admin/includes/class-wp-upgrader.php
index fd70ba469e..71591d60a3 100644
--- a/wp-admin/includes/class-wp-upgrader.php
+++ b/wp-admin/includes/class-wp-upgrader.php
@@ -342,7 +342,8 @@ class WP_Upgrader {
 			if ( ! empty( $details['files'] ) ) {
 				$children = $this->flatten_dirlist( $details['files'], $path . $name . '/' );
 
-				$files = array_merge( $files, $children );
+				// Merge keeping possible numeric keys, which array_merge() will reindex from 0..n
+				$files = $files + $children;
 			}
 		}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 3dbf58a7ac..7151de9e83 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42211';
+$wp_version = '5.0-alpha-42214';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.