diff --git a/readme.md b/readme.md
index ee20bdb..3621d4e 100644
--- a/readme.md
+++ b/readme.md
@@ -255,7 +255,7 @@ is.urlInstance(url);
 //=> true
 ```
 
-### .urlString(value)
+##### .urlString(value)
 
 Returns `true` if `value` is a URL string.