--- a/toolkit/components/extensions/test/xpcshell/test_ext_management_uninstall_self.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_management_uninstall_self.js
@@ -14,17 +14,17 @@ const manifest = {
     gecko: {
       id,
     },
   },
   name: "test extension name",
   version: "1.0",
 };
 
-const waitForUninstalled = new Promise(resolve => {
+const waitForUninstalled = () => new Promise(resolve => {
   const listener = {
     onUninstalled: (addon) => {
       equal(addon.id, id, "The expected add-on has been uninstalled");
       AddonManager.getAddonByID(addon.id, checkedAddon => {
         equal(checkedAddon, null, "Add-on no longer exists");
         AddonManager.removeAddonListener(listener);
         resolve();
       });
@@ -62,17 +62,17 @@ add_task(function* test_management_unins
     background,
     useAddonManager: "temporary",
   });
 
   yield extension.startup();
   let addon = yield promiseAddonByID(id);
   notEqual(addon, null, "Add-on is installed");
   extension.sendMessage("uninstall");
-  yield waitForUninstalled;
+  yield waitForUninstalled();
   yield extension.markUnloaded();
   Services.obs.notifyObservers(extension.extension.file, "flush-cache-entry", null);
 });
 
 add_task(function* test_management_uninstall_prompt_uninstall() {
   promptService._response = 0;
 
   function background() {
@@ -86,17 +86,17 @@ add_task(function* test_management_unins
     background,
     useAddonManager: "temporary",
   });
 
   yield extension.startup();
   let addon = yield promiseAddonByID(id);
   notEqual(addon, null, "Add-on is installed");
   extension.sendMessage("uninstall");
-  yield waitForUninstalled;
+  yield waitForUninstalled();
   yield extension.markUnloaded();
 
   // Test localization strings
   equal(promptService._confirmExArgs[1], `Uninstall ${manifest.name}`);
   equal(promptService._confirmExArgs[2],
         `The extension “${manifest.name}” is requesting to be uninstalled. What would you like to do?`);
   equal(promptService._confirmExArgs[4], "Uninstall");
   equal(promptService._confirmExArgs[5], "Keep Installed");