Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 26862)
+++ wp-includes/media.php	(working copy)
@@ -724,7 +724,7 @@
 			unset( $attr['orderby'] );
 	}
 
-	extract(shortcode_atts(array(
+	$defaults_atts = array(
 		'order'      => 'ASC',
 		'orderby'    => 'menu_order ID',
 		'id'         => $post ? $post->ID : 0,
@@ -735,8 +735,18 @@
 		'size'       => 'thumbnail',
 		'include'    => '',
 		'exclude'    => '',
-		'link'       => ''
-	), $attr, 'gallery'));
+		'link'       => '',
+	);
+
+	if ( current_theme_supports( 'html5', 'gallery' ) ) {
+		$defaults_atts = wp_parse_args( array(
+			'itemtag'    => 'figure',
+			'icontag'    => 'div',
+			'captiontag' => 'figcaption',
+		), $defaults_atts );
+	}
+
+	extract( shortcode_atts( $defaults_atts, $attr, 'gallery' ) );
 
 	$id = intval($id);
 	if ( 'RAND' == $order )