--- a/browser/components/extensions/test/browser/browser_ext_popup_sendMessage.js
+++ b/browser/components/extensions/test/browser/browser_ext_popup_sendMessage.js
@@ -18,17 +18,17 @@ add_task(function* test_popup_sendMessag
       },
     },
 
     files: {
       "popup.html": scriptPage("popup.js"),
       "popup.js": async function() {
         browser.runtime.onMessage.addListener(async msg => {
           if (msg == "popup-ping") {
-            return Promise.resolve("popup-pong");
+            return "popup-pong";
           }
         });
 
         let response = await browser.runtime.sendMessage("background-ping");
         browser.test.sendMessage("background-ping-response", response);
       },
     },