diff --git a/site/test/setup/msw.ts b/site/test/setup/msw.ts
index 2458492c296..a42e582ec88 100644
--- a/site/test/setup/msw.ts
+++ b/site/test/setup/msw.ts
@@ -8,4 +8,14 @@ afterEach(() => {
 	server.resetHandlers();
 	vi.clearAllMocks();
 });
-afterAll(() => server.close());
+afterAll(async () => {
+	// A leftover fake clock would make the timer flush below hang.
+	if (vi.isFakeTimers()) {
+		vi.useRealTimers();
+	}
+	// Radix FocusScope defers its unmount dispatch with setTimeout(0). Flush
+	// it before vitest tears down the jsdom environment, where it would throw
+	// an unhandled "parameter 1 is not of type 'Event'" TypeError.
+	await new Promise((resolve) => setTimeout(resolve, 0));
+	server.close();
+});