Index: src/wp-includes/theme.php
===================================================================
--- src/wp-includes/theme.php	(revision 27400)
+++ src/wp-includes/theme.php	(working copy)
@@ -1398,7 +1398,8 @@
 		case 'html5' :
 			// You can't just pass 'html5', you need to pass an array of types.
 			if ( empty( $args[0] ) ) {
-				$args = array( 0 => array( 'comment-list', 'comment-form', 'search-form' ) );
+				_doing_it_wrong( "add_theme_support( 'html5' )", 'You need to pass an array of types.', '3.6.1' );
+				$args = array( 0 => array( 'comment-list', 'comment-form', 'search-form' ) ); // Back compat
 			} elseif ( ! is_array( $args[0] ) ) {
 				_doing_it_wrong( "add_theme_support( 'html5' )", 'You need to pass an array of types.', '3.6.1' );
 				return false;