--- a/browser/extensions/formautofill/test/browser/browser_autocomplete_marked_detached_tab.js
+++ b/browser/extensions/formautofill/test/browser/browser_autocomplete_marked_detached_tab.js
@@ -22,16 +22,17 @@ add_task(async function setup_storage() 
 
 add_task(async function test_detach_tab_marked() {
   await BrowserTestUtils.withNewTab({gBrowser, url: URL}, async function(browser) {
     const {autoCompletePopup} = browser;
 
     // Check the page after the initial load
     await openPopupOn(browser, "#street-address");
     checkPopup(autoCompletePopup);
+    await closePopup(browser);
 
     // Detach the tab to a new window
     let newWin = gBrowser.replaceTabWithWindow(gBrowser.getTabForBrowser(browser));
     await TestUtils.topicObserved("browser-delayed-startup-finished", subject => {
       return subject == newWin;
     });
 
     info("tab was detached");