diff --git a/js/navigation.js b/js/navigation.js
index 22afbb6cf..2932105a2 100644
--- a/js/navigation.js
+++ b/js/navigation.js
@@ -88,7 +88,7 @@ function PMA_setFrameSize()
 {
     pma_navi_width = PMA_getCookie('pma_navi_width');
     //alert('from cookie: ' + typeof(pma_navi_width) + ' : ' + pma_navi_width);
-    if (pma_navi_width != null) {
+    if (pma_navi_width != null && parent.document != document) {
         if (parent.text_dir == 'ltr') {
             parent.document.getElementById('mainFrameset').cols = pma_navi_width + ',*';
         } else {