diff --git a/browser/components/sidebar/browser-sidebar.js b/browser/components/sidebar/browser-sidebar.js
index 220c3c83fa09daaec433803a4655a20114a137a6..1ef8adc3ecfa61839bb993f7fc090133bffe77db 100644
--- a/browser/components/sidebar/browser-sidebar.js
+++ b/browser/components/sidebar/browser-sidebar.js
@@ -793,7 +793,7 @@ 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;
     });