diff --git a/flow.md b/flow.md
index c5bc83b1f..ca63eca73 100644
--- a/flow.md
+++ b/flow.md
@@ -133,7 +133,7 @@ type Album = {
 ```js
 const a: Album = { } // ✓ OK
 a.name = 'Blue'      // ✓ OK
-a.name = null        // ✓ OK
+a.name = null        // ✓ Error
 a.name = undefined   // ✓ OK
 ```