diff --git a/.changeset/sharp-frogs-bathe.md b/.changeset/sharp-frogs-bathe.md
new file mode 100644
index 00000000..55eccbf8
--- /dev/null
+++ b/.changeset/sharp-frogs-bathe.md
@@ -0,0 +1,5 @@
+---
+'@remote-dom/react': patch
+---
+
+Apply React polyfill directly to `globalThis`
diff --git a/packages/react/source/polyfill.ts b/packages/react/source/polyfill.ts
index c575bf54..74951f65 100644
--- a/packages/react/source/polyfill.ts
+++ b/packages/react/source/polyfill.ts
@@ -1,7 +1,25 @@
-import {window} from '@remote-dom/core/polyfill';
-
 class HTMLIFrameElement extends HTMLElement {}
 
+// React checks whether elements are Iframes on initialization.
+defineGlobalProperty('HTMLIFrameElement', {
+  value: HTMLIFrameElement,
+  configurable: true,
+});
+
+// React ues the `location` and `navigator` properties when printing help text in
+// development, and the `Window` polyfill from Remote DOM doesn’t define these properties.
+// We copy their implementation from the existing global scope when it exists, and
+// provide a minimal working implementation otherwise.
+defineGlobalProperty('location', {
+  value: globalThis.location ?? {protocol: 'https:'},
+  configurable: true,
+});
+
+defineGlobalProperty('navigator', {
+  value: globalThis.navigator ?? {userAgent: ''},
+  configurable: true,
+});
+
 class CSSStyleDeclaration {
   getPropertyValue(_key: string): string | null | undefined {
     return undefined;
@@ -24,27 +42,6 @@ class CSSStyleDeclaration {
   }
 }
 
-// React ues the `location` property when printing help text in development.
-if (!window.location) {
-  Object.defineProperty(window, 'location', {
-    value: globalThis.location ?? {protocol: 'https:'},
-    configurable: true,
-  });
-}
-
-if (!window.navigator) {
-  Object.defineProperty(window, 'navigator', {
-    value: globalThis.navigator ?? {userAgent: ''},
-    configurable: true,
-  });
-}
-
-// React checks whether elements are Iframes on initialization.
-Object.defineProperty(window, 'HTMLIFrameElement', {
-  value: HTMLIFrameElement,
-  configurable: true,
-});
-
 // React checks for a few properties in `document.createElement('div').style`
 const STYLE = Symbol('style');
 Object.defineProperty(Element.prototype, 'style', {
@@ -61,3 +58,10 @@ Object.defineProperty(Element.prototype, 'style', {
     this.style.cssText = String(cssText);
   },
 });
+
+function defineGlobalProperty(name: string, descriptor: PropertyDescriptor) {
+  Object.defineProperty(window, name, descriptor);
+  Object.defineProperty(globalThis, name, descriptor);
+}
+
+export {};