diff --git a/README.md b/README.md
index 0f6ed71..9eab6d1 100644
--- a/README.md
+++ b/README.md
@@ -17,3 +17,6 @@ $entity->metadata->set("name", "PCM");
 $entity->metadata->get("name"); // "PCM"
 $entity->metadata->isSet("name"); // true
 ```
+
+> Like setting a property normally, setting metadata values will not automatically update the database.
+You must call `flush()` from the `EntityManager` as usual when you wish to persist data.