Index: src/wp-includes/post-template.php
===================================================================
--- src/wp-includes/post-template.php	(revision 31863)
+++ src/wp-includes/post-template.php	(working copy)
@@ -675,6 +675,9 @@
 			$classes[] = 'post-type-paged-' . $page;
 	}
 
+	$locale = get_locale();
+	$classes[] = 'locale-' . $locale;
+
 	if ( ! empty( $class ) ) {
 		if ( !is_array( $class ) )
 			$class = preg_split( '#\s+#', $class );