diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js b/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
index 386191422c64..29a9e4ff4dae 100644
--- a/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
@@ -6,9 +6,26 @@ const STARTUP_APIS = [
   "backgroundPage",
 ];
 
-// Tests that only the minimal set of API scripts are loaded at startup
-// for a simple extension.
-add_task(async function test_loaded_api_scripts() {
+const STARTUP_MODULES = [
+  "resource://gre/modules/Extension.jsm",
+  "resource://gre/modules/ExtensionCommon.jsm",
+  "resource://gre/modules/ExtensionParent.jsm",
+  // FIXME: This is only loaded at startup for new extension installs.
+  // Otherwise the data comes from the startup cache. We should test for
+  // this.
+  "resource://gre/modules/ExtensionPermissions.jsm",
+  "resource://gre/modules/ExtensionUtils.jsm",
+];
+
+if (!Services.prefs.getBoolPref("extensions.webextensions.remote")) {
+  STARTUP_MODULES.push(
+    "resource://gre/modules/ExtensionChild.jsm",
+    "resource://gre/modules/ExtensionPageChild.jsm");
+}
+
+// Tests that only the minimal set of API scripts and modules are loaded at
+// startup for a simple extension.
+add_task(async function test_loaded_scripts() {
   await ExtensionTestUtils.startAddonManager();
 
   let extension = ExtensionTestUtils.loadExtension({
@@ -28,5 +45,13 @@ add_task(async function test_loaded_api_scripts() {
   deepEqual(loadedAPIs.sort(), STARTUP_APIS,
             "No extra APIs should be loaded at startup for a simple extension");
 
+
+  const loader = Cc["@mozilla.org/moz/jsloader;1"].getService(Ci.xpcIJSModuleLoader);
+  let loadedModules = loader.loadedModules()
+                            .filter(url => url.startsWith("resource://gre/modules/Extension"));
+
+  deepEqual(loadedModules.sort(), STARTUP_MODULES.sort(),
+            "No extra extension modules should be loaded at startup for a simple extension");
+
   await extension.unload();
 });