diff --git a/scripts/gendoc.py b/scripts/gendoc.py
index 57a04717..e3c3797e 100755
--- a/scripts/gendoc.py
+++ b/scripts/gendoc.py
@@ -79,9 +79,11 @@ if __name__ == '__main__':
         # we accept almost no args, so they don't know what they're doing!
         print "gendoc.py - Generate the Matrix specification as HTML."
         print "Usage:"
-        print "  python gendoc.py"
+        print "  python gendoc.py [--nodelete]"
         print ""
         print "The specification can then be found in the gen/ folder."
+        print ("If --nodelete was specified, intermediate files will be "
+               "present in the tmp/ folder.")
         print ""
         print "Requirements:"
         print " - This script requires Jinja2 and rst2html (docutils)."