Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 26667)
+++ wp-includes/theme.php	(working copy)
@@ -489,6 +489,7 @@
 	}
 
 	asort( $found_themes );
+	$found_themes = apply_filters( 'found_themes', $found_themes );
 
 	$theme_roots = array();
 	$relative_theme_roots = array_flip( $relative_theme_roots );