--- a/browser/components/contextualidentity/test/browser/browser_forgetaboutsite.js
+++ b/browser/components/contextualidentity/test/browser/browser_forgetaboutsite.js
@@ -238,25 +238,25 @@ function* test_storage_cleared() {
   for (let userContextId of Object.keys(USER_CONTEXTS)) {
     // Load the page in 3 different contexts and set the local storage
     // which should only be visible in that context.
     let value = USER_CONTEXTS[userContextId];
 
     // Open our tab in the given user context.
     let tabInfo = yield* openTabInUserContext(TEST_URL+ "file_set_storages.html?" + value, userContextId);
 
-    // Check that the local storage has been set correctly.
-    let win = tabInfo.browser.contentWindow;
-    Assert.equal(win.localStorage.getItem("userContext"), USER_CONTEXTS[userContextId], "Check the local storage value");
+    // Check that the storages has been set correctly.
+    yield ContentTask.spawn(tabInfo.browser, { userContext: USER_CONTEXTS[userContextId] }, function* (arg) {
+      // Check that the local storage has been set correctly.
+      Assert.equal(content.localStorage.getItem("userContext"), arg.userContext, "Check the local storage value");
 
-    // Check that the session storage has been set correctly.
-    Assert.equal(win.sessionStorage.getItem("userContext"), USER_CONTEXTS[userContextId], "Check the session storage value");
+      // Check that the session storage has been set correctly.
+      Assert.equal(content.sessionStorage.getItem("userContext"), arg.userContext, "Check the session storage value");
 
-    // Check that the indexedDB has been set correctly.
-    yield ContentTask.spawn(tabInfo.browser, { userContext: USER_CONTEXTS[userContextId] }, function* (arg) {
+      // Check that the indexedDB has been set correctly.
       let request = content.indexedDB.open("idb", 1);
 
       let db = yield new Promise(done => {
         request.onsuccess = event => {
           done(event.target.result);
         };
       });
 
@@ -280,26 +280,26 @@ function* test_storage_cleared() {
   // Forget the site.
   ForgetAboutSite.removeDataFromDomain(TEST_HOST);
 
   // Open the tab again without setting the localStorage and check that the
   // local storage has been cleared or not.
   for (let userContextId of Object.keys(USER_CONTEXTS)) {
     // Open our tab in the given user context without setting local storage.
     let tabInfo = yield* openTabInUserContext(TEST_URL+ "file_set_storages.html", userContextId);
-    let win = tabInfo.browser.contentWindow;
-
-    // Check that does the local storage be cleared or not.
-    Assert.ok(!win.localStorage.getItem("userContext"), "The local storage has been cleared");
 
-    // Check that does the session storage be cleared or not.
-    Assert.ok(!win.sessionStorage.getItem("userContext"), "The session storage has been cleared");
+    // Check that do storages be cleared or not.
+    yield ContentTask.spawn(tabInfo.browser, null, function* () {
+      // Check that does the local storage be cleared or not.
+      Assert.ok(!content.localStorage.getItem("userContext"), "The local storage has been cleared");
 
-    // Check that does the indexedDB be cleared or not.
-    yield ContentTask.spawn(tabInfo.browser, null, function* () {
+      // Check that does the session storage be cleared or not.
+      Assert.ok(!content.sessionStorage.getItem("userContext"), "The session storage has been cleared");
+
+      // Check that does the indexedDB be cleared or not.
       let request = content.indexedDB.open("idb", 1);
 
       let db = yield new Promise(done => {
         request.onsuccess = event => {
           done(event.target.result);
         };
       });
       try {