From be22909d809666da1e7efe6428a500e1f4f76933 Mon Sep 17 00:00:00 2001
From: Mantas Kantautas <mantas.kantautas@gmail.com>
Date: Fri, 23 Oct 2026 03:53:05 +0300
Subject: [PATCH] fix: Avoid `cleanup` error when the container is `document`

---
 src/__tests__/cleanup.js | 40 ++++++++++++++++++++++++++++++++++++++++
 src/pure.js              |  3 ++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/src/__tests__/cleanup.js b/src/__tests__/cleanup.js
index 9f17c722..649a34e8 100644
--- a/src/__tests__/cleanup.js
+++ b/src/__tests__/cleanup.js
@@ -27,6 +27,46 @@ test('cleanup does not error when an element is not a child', () => {
   cleanup()
 })
 
+describe('container is the document', () => {
+  let documentElement
+  beforeEach(() => {
+    documentElement = document.documentElement
+  })
+
+  afterEach(() => {
+    // React 18 removes the `<html>` element when unmounting a root rendered into `document`
+    if (document.documentElement === null) {
+      document.appendChild(documentElement)
+    }
+  })
+
+  test('cleanup does not error when the container is the document', () => {
+    render(
+      <html lang="en">
+        <body>
+          <div />
+        </body>
+      </html>,
+      {container: document},
+    )
+
+    cleanup()
+  })
+
+  test('cleanup does not error when hydrating the document', () => {
+    render(
+      // eslint-disable-next-line jsx-a11y/html-has-lang -- matches the existing document
+      <html>
+        <head />
+        <body />
+      </html>,
+      {container: document, hydrate: true},
+    )
+
+    cleanup()
+  })
+})
+
 test('cleanup runs effect cleanup functions', () => {
   const spy = jest.fn()
 
diff --git a/src/pure.js b/src/pure.js
index 3ea36bfe..c745c855 100644
--- a/src/pure.js
+++ b/src/pure.js
@@ -319,7 +319,8 @@ function cleanup() {
     act(() => {
       root.unmount()
     })
-    if (container.parentNode === document.body) {
+    // `document.body` is `null` if unmounting a root rendered into `document` removed `<html>` (React 18)
+    if (document.body !== null && container.parentNode === document.body) {
       document.body.removeChild(container)
     }
   })