--- a/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_open.html
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_open.html
@@ -51,16 +51,20 @@ add_task(async function test_downloads_o
 
   let extension = ExtensionTestUtils.loadExtension(extensionData);
   await extension.startup();
   await extension.awaitFinish("downloads tests");
   await extension.unload();
 });
 
 add_task(async function downloads_open_invalid_id() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.webextensions.remote", false]],
+  });
+
   async function pageScript() {
     window.addEventListener("keypress", async function handler() {
       try {
         await browser.downloads.open(10);
         browser.test.sendMessage("download-open.result", {success: true});
       } catch (e) {
         browser.test.sendMessage("download-open.result", {
           success: false,

--- a/toolkit/components/extensions/test/mochitest/test_chrome_ext_permissions.html
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_permissions.html
@@ -152,17 +152,18 @@ function makeTest(manifestPermissions, o
 
     await extension.unload();
   };
 }
 
 add_task(function setup() {
   // Don't bother with prompts in this test.
   return SpecialPowers.pushPrefEnv({
-    set: [["extensions.webextOptionalPermissionPrompts", false]],
+    set: [["extensions.webextensions.remote", false],
+          ["extensions.webextOptionalPermissionPrompts", false]],
   });
 });
 
 const ORIGIN = "*://example.com/";
 add_task(makeTest([], {
   permissions: ["cookies"],
   origins: [ORIGIN],
 }));