diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index 6374a25e9dc1..ffe5e9db32a7 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -1543,7 +1543,7 @@
               if ("owner" in aTab && aTab.owner &&
                   this.mPrefs.getBoolPref("browser.tabs.selectOwnerOnClose")) {
                 for (var i = 0; i < length; ++i) {
-                  tab = this.mTabContainer.childNodes[i];
+                  var tab = this.mTabContainer.childNodes[i];
                   if (tab == aTab.owner) {
                     newIndex = i;
                     break;