diff --git a/README.md b/README.md
index 94f08d1..732a6df 100644
--- a/README.md
+++ b/README.md
@@ -81,7 +81,7 @@ The returned `url` instance contains the following properties:
 - `username`: Username of basic authentication.
 - `password`: Password of basic authentication.
 - `host`: Host name with port number.
-- `hostname`: Host name without port number.
+- `hostname`: Host name without port number. This might be an invalid hostname.
 - `port`: Optional port number.
 - `pathname`: URL path.
 - `query`: Parsed object containing query string, unless parsing is set to false.