diff --git a/examples/react/optimistic-updates-ui/src/pages/index.tsx b/examples/react/optimistic-updates-ui/src/pages/index.tsx
index 18f9bd8714..7e4a8e4b12 100644
--- a/examples/react/optimistic-updates-ui/src/pages/index.tsx
+++ b/examples/react/optimistic-updates-ui/src/pages/index.tsx
@@ -39,6 +39,9 @@ function Example() {
         body: JSON.stringify({ text: newTodo }),
         headers: { 'Content-Type': 'application/json' },
       })
+      if (!response.ok) {
+        throw new Error('Something went wrong.')
+      }
       return await response.json()
     },
     onSettled: () => queryClient.invalidateQueries({ queryKey: ['todos'] }),