diff --git a/ui/webui/resources/br_elements/br_toolbar/br_toolbar.ts b/ui/webui/resources/br_elements/br_toolbar/br_toolbar.ts
index e358b317d4bf..684dfb558341 100644
--- a/ui/webui/resources/br_elements/br_toolbar/br_toolbar.ts
+++ b/ui/webui/resources/br_elements/br_toolbar/br_toolbar.ts
@@ -207,7 +207,7 @@ export class CrToolbarElement extends CrLitElement {
   initSlotFilledDetection() {
     // Style the 'extra items' slot only if it contains
     // content.
-    const toolbarExtraElement = this.querySelector('.toolbar-extra')
+    const toolbarExtraElement = this.shadowRoot!.querySelector('.toolbar-extra')
     if (!toolbarExtraElement) {
       console.error('Could not find "toolbar-extra" element')
       return