diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index b2b7ba48ae..ba968bca8f 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -393,7 +393,7 @@ function search_theme_directories( $force = false ) {
 				if ( ! $sub_dirs )
 					return false;
 				foreach ( $sub_dirs as $sub_dir ) {
-					if ( ! is_dir( $theme_root . '/' . $dir ) || $dir[0] == '.' || $dir == 'CVS' )
+					if ( ! is_dir( $theme_root . '/' . $dir . '/' . $sub_dir ) || $dir[0] == '.' || $dir == 'CVS' )
 						continue;
 					if ( ! file_exists( $theme_root . '/' . $dir . '/' . $sub_dir . '/style.css' ) )
 						continue;