diff --git a/lib/yui/blocks/blocks.js b/lib/yui/blocks/blocks.js
index bff92ee735c..f6fbf82531f 100644
--- a/lib/yui/blocks/blocks.js
+++ b/lib/yui/blocks/blocks.js
@@ -102,7 +102,7 @@ YUI.add('moodle-core-blocks', function(Y) {
             var region = node.ancestor('div.'+CSS.BLOCKREGION).get('id').replace(/region-/i, '');
             if (Y.Array.indexOf(this.get('regions'), region) === -1) {
                 // Must be standard side-X
-                if (right_to_left()) {
+                if (Y.one('body').hasClass('dir-rtl')) {
                     if (region == 'post') {
                         region = 'pre';
                     } else if (region == 'pre') {