diff --git a/config.md b/config.md
index 47da513cc..f5b6a148f 100644
--- a/config.md
+++ b/config.md
@@ -154,6 +154,7 @@ _Note: symbolic name for uid and gid, such as uname and gname respectively, are
 }
 ```
 
+If left empty, the user id and group id both defaults to 0 (root), and no additional group IDs are added.
 
 ## Hostname