diff --git a/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/react-dom_v18.x.x.js b/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/react-dom_v18.x.x.js
index 02abe5a995..d49eebec65 100644
--- a/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/react-dom_v18.x.x.js
+++ b/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/react-dom_v18.x.x.js
@@ -127,6 +127,8 @@ declare module 'react-dom' {
 
   declare function unmountComponentAtNode(container: any): boolean;
 
+  declare function flushSync(callback: () => mixed): void;
+
   declare function unstable_batchedUpdates<A, B, C, D, E>(
     callback: (a: A, b: B, c: C, d: D, e: E) => mixed,
     a: A,
diff --git a/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/test_react-dom_v18.x.x.js b/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/test_react-dom_v18.x.x.js
index d4424c8ece..b4682e42a8 100644
--- a/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/test_react-dom_v18.x.x.js
+++ b/definitions/npm/react-dom_v18.x.x/flow_v0.127.x-/test_react-dom_v18.x.x.js
@@ -151,6 +151,10 @@ ReactDOM.render(<Example2 />, test$querySelector('#site'), '');
 // $FlowExpectedError[incompatible-call]
 ReactDOM.render(<Example2 />, test$querySelector('#site'), null);
 
+(ReactDOM.flushSync(() => ''): void);
+// $FlowExpectedError[incompatible-call]
+ReactDOM.flushSync();
+
 describe('react-dom/client', () => {
   describe('createRoot', () => {
     it('works', () => {