RockRidge can be -R or -r.
diff --git a/README b/README
index 27e50ce..588a8fa 100644
--- a/README
+++ b/README
@@ -16,8 +16,9 @@
mkisofs -z -R [other options] -o compressed.iso compressed_dir
-IMPORTANT: you *must* use RockRidge (-R) since this is an extensions
-to the RockRidge specification. Without the -R, -z will have no effect.
+IMPORTANT: you *must* enable RockRidge (-R or -r) since this is an
+extensions to the RockRidge specification. Without RockRidge, -z will
+have no effect.
Note that if there are files you do not want compressed (for example,
files involved in booting, or README files you want to be readable
