diff --git a/packages/react-dom/src/__tests__/ReactDOMServerIntegrationBasic-test.js b/packages/react-dom/src/__tests__/ReactDOMServerIntegrationBasic-test.js
index a0793a6215b66..2821dd088bb48 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerIntegrationBasic-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerIntegrationBasic-test.js
@@ -15,7 +15,7 @@ const ReactDOMServerIntegrationUtils = require('./utils/ReactDOMServerIntegratio
 const TEXT_NODE_TYPE = 3;
 
 let React;
-let ReactDOM;
+let ReactDOMClient;
 let ReactDOMServer;
 let ReactTestUtils;
 
@@ -23,13 +23,13 @@ function initModules() {
   // Reset warning cache.
   jest.resetModules();
   React = require('react');
-  ReactDOM = require('react-dom');
+  ReactDOMClient = require('react-dom/client');
   ReactDOMServer = require('react-dom/server');
   ReactTestUtils = require('react-dom/test-utils');
 
   // Make them available to the helpers.
   return {
-    ReactDOM,
+    ReactDOMClient,
     ReactDOMServer,
     ReactTestUtils,
   };
@@ -149,8 +149,10 @@ describe('ReactDOMServerIntegration', () => {
       expect(await render([])).toBe(null);
       expect(await render(false)).toBe(null);
       expect(await render(true)).toBe(null);
-      expect(await render(undefined)).toBe(null);
       expect(await render([[[false]], undefined])).toBe(null);
+
+      // hydrateRoot errors for undefined children.
+      expect(await render(undefined, 1)).toBe(null);
     });
   });
 });