diff --git a/zephyr/static/js/ui.js b/zephyr/static/js/ui.js
index d2d7507cba..e8ded192a7 100644
--- a/zephyr/static/js/ui.js
+++ b/zephyr/static/js/ui.js
@@ -133,7 +133,7 @@ function resizehandler(e) {
         sidebar_nav.width('');
     }
 
-    $("#bottom_whitespace").height($(window).height() * 0.4);
+    $("#bottom_whitespace").height(viewport.height() * 0.4);
     $("#main_div").css('min-height', viewport.height());
 
     // This function might run onReady (if we're in a narrow window),