diff --git a/config.md b/config.md
index a3c132ae3..4207f5338 100644
--- a/config.md
+++ b/config.md
@@ -104,7 +104,7 @@ For Linux-based systems the user structure has the following fields:
 
 ## Hostname
 
-* **`hostname`** (string, optional) as it is accessible to processes running inside.  On Linux, you can only set this if your bundle creates a new [UTS namespace][uts-namespace].
+* **`hostname`** (string, optional) as it is accessible to processes running inside.  On Linux, you can only set and MUST set this if your bundle creates a new [UTS namespace][uts-namespace].
 
 *Example*