diff --git a/docs/config/index.md b/docs/config/index.md
index bb02c636b..33dd7d8da 100644
--- a/docs/config/index.md
+++ b/docs/config/index.md
@@ -11,14 +11,30 @@ General configuration options for QUnit.
 
 ## Preconfiguring QUnit
 
-If you load QUnit asynchronously or otherwise need to configure QUnit before it is loaded, you can define the global variable `QUnit` with a `config` property. Any other properties of the QUnit object will be ignored. The config values specified here will be carried over to the real `QUnit.config` object.
+If you load QUnit asynchronously or otherwise need to configure QUnit before it is loaded, you can predefine the configuration by creating a global variable `QUnit` with a `config` property.
+
+The config values specified here will be carried over to the real `QUnit.config` object. Any other properties of this object will be ignored.
 
 ```js
-// Before QUnit is loaded
-window.QUnit = {
+// Implicit global
+// Supported everywhere, including old browsers. (But not ES strict mode.)
+QUnit = {
   config: {
     autostart: false,
-    noglobals: true
+    maxDepth: 12
   }
 };
+
+// Browser global
+// For all browsers (including strict mode and old browsers)
+window.QUnit = { /* .. */ };
+
+// Isomorphic global
+// For modern browsers, SpiderMonkey, and Node.js (incl. strict mode).
+globalThis.QUnit = { /* .. */ };
 ```
+
+### Changelog
+
+| UNRELEASED | Preconfig support added for SpiderMonkey and other environments.<br/>Previously, it was limited to the browser environment.
+| [QUnit 2.1.0](https://github.com/qunitjs/qunit/releases/tag/2.1.0) | Preconfig feature introduced.
diff --git a/src/core/config.js b/src/core/config.js
index 0570177cc..1e095451a 100644
--- a/src/core/config.js
+++ b/src/core/config.js
@@ -1,4 +1,4 @@
-import { window, localSessionStorage } from '../globals';
+import { globalThis, localSessionStorage } from '../globals';
 import { extend } from './utilities';
 
 /**
@@ -103,12 +103,13 @@ const config = {
   storage: localSessionStorage
 };
 
-// take a predefined QUnit.config and extend the defaults
-const globalConfig = window && window.QUnit && window.QUnit.config;
-
-// only extend the global config if there is no QUnit overload
-if (window && window.QUnit && !window.QUnit.version) {
-  extend(config, globalConfig);
+// Apply a predefined QUnit.config object
+//
+// Ignore QUnit.config if it is a QUnit distribution instead of preconfig.
+// That means QUnit was loaded twice! (Use the same approach as export.js)
+const preConfig = globalThis && globalThis.QUnit && !globalThis.QUnit.version && globalThis.QUnit.config;
+if (preConfig) {
+  extend(config, preConfig);
 }
 
 // Push a loose unnamed module to the modules collection
diff --git a/test/preconfigured.js b/test/preconfigured.js
index 096d8ff1c..cdec93768 100644
--- a/test/preconfigured.js
+++ b/test/preconfigured.js
@@ -1,21 +1,14 @@
 /* eslint-env browser */
-window.addEventListener('load', function () {
-  // make sure QUnit has started if autostart would be true
-  setTimeout(function () {
-    QUnit.module('QUnit.preconfigured.asyncTests');
-    QUnit.test('QUnit.config should have an expected default', function (assert) {
-      assert.true(QUnit.config.scrolltop, 'The scrolltop default is true');
-    });
+QUnit.module('QUnit.config [preconfigured]');
 
-    QUnit.test('Qunit.config.reorder default was overwritten', function (assert) {
-      assert.false(QUnit.config.reorder, 'reorder was overwritten');
-    });
-
-    QUnit.start();
-  }, 100);
+QUnit.test('config', function (assert) {
+  assert.strictEqual(QUnit.config.maxDepth, 5, 'maxDepth default');
+  assert.false(QUnit.config.autostart, 'autostart override');
+  assert.false(QUnit.config.reorder, 'reorder override');
 });
 
-QUnit.module('QUnit.preconfigured');
-QUnit.test('Autostart is false', function (assert) {
-  assert.false(QUnit.config.autostart, 'The global autostart setting is applied');
+window.addEventListener('load', function () {
+  setTimeout(function () {
+    QUnit.start();
+  }, 1);
 });