diff --git a/browser/base/content/browser-tabPreviews.js b/browser/base/content/browser-tabPreviews.js
index 479000ae9bac..8a5bf76c1932 100644
--- a/browser/base/content/browser-tabPreviews.js
+++ b/browser/base/content/browser-tabPreviews.js
@@ -820,15 +820,18 @@ var allTabs = {
       this.container.appendChild(document.createElement("hbox"));
 
     var row = this.container.firstChild;
-    var i = 0;
+    var colCount = 0;
     previews.forEach(function (preview) {
+      if (!preview.hidden &&
+          ++colCount > this._columns) {
+        row = row.nextSibling;
+        colCount = 1;
+      }
       preview.setAttribute("minwidth", outerWidth);
       preview.setAttribute("height", outerHeight);
       preview.setAttribute("canvasstyle", canvasStyle);
       preview.removeAttribute("closebuttonhover");
       row.appendChild(preview);
-      if (!preview.hidden)
-        row = this.container.childNodes[Math.floor(++i / this._columns)];
     }, this);
 
     this._stack.width = maxWidth;