diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index ecbedec482..662df894b3 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -413,6 +413,8 @@ function register_theme_directory( $directory ) {
 		$wp_theme_directories[] = $untrailed;
 	}
 
+	wp_clean_themes_cache();
+
 	return true;
 }
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 98c4d440f1..a2ff12e12b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42787';
+$wp_version = '5.0-alpha-42788';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.