diff --git a/README.md b/README.md
index 381a05a..fa6e8d4 100644
--- a/README.md
+++ b/README.md
@@ -102,7 +102,6 @@ Usage: isabelle DOF_mkroot [OPTIONS] [DIR]
 
   Options are:
     -h           print this help text and exit
-    -d           enable document preparation
     -n NAME      alternative session name (default: DIR base name)
     -o ONTOLOGY  (default: core)
        Available ontologies: