diff --git a/README.md b/README.md
index 238e5c12a2d9a3d534f8e56fd3755ea870f6bedd..312b626308e000b3f37fa354513b5aef500007f3 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ To deploy this role to a managed host, the following software must be installed
 * Python3
 * SSHd
 
-In order to create a bootable ISO image, you have to provide a RHEL ISO image in the role's root directory and set the correct version in `vars/main.yml`.
+In order to create a bootable ISO image, you have to provide a RHEL ISO image (named something like `rhel-server-7.9-x86_64-dvd.iso`) in the role's root directory and set the correct version in `vars/main.yml`. Just using the `rhel-server-7.9-x86_64-boot.iso` does NOT work.
 
 ## Quick start