diff --git a/browser/components/sidebar/browser-sidebar.js b/browser/components/sidebar/browser-sidebar.js
index f62decaa3f7400787b245b3e765197f4e70dffbb..329240cf434fdbefcf145a733179bd565a814280 100644
--- a/browser/components/sidebar/browser-sidebar.js
+++ b/browser/components/sidebar/browser-sidebar.js
@@ -779,7 +779,7 @@ var SidebarController = {
   setPosition() {
     // First reset all ordinals to match DOM ordering.
     let contentArea = document.getElementById("tabbrowser-tabbox");
-    let browser = document.getElementById("browser");
+    let browser = document.getElementById("tabbrowser-tabbox");
     [...browser.children].forEach((node, i) => {
       node.style.order = i + 1;
     });